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The story of Southwest's legal fight was turned into a children's book, Gumwrappers and Goggles by Winifred Barnum in 1983. In the story, TJ Love, a small jet, is taken to court by two larger jets to keep him from their hangar, and then to try and stop him from flying at all. Taken to court, TJ Love's right to fly is upheld after an impassioned plea from The Lawyer. While no company names are mentioned in the book, TJ Love's colors are those of Southwest Airlines, and the two other jets are colored in Braniff and Continental's colors. The Lawyer is designed to resemble Herb Kelleher. The book was adapted into a stage musical, Show your Spirit, sponsored by Southwest Airlines, and played only in towns serviced by the airline.[8] Southwest Airlines founder Herb Kelleher studied California-based Pacific Southwest Airlines extensively and used many of the airline's ideas to form the corporate culture at Southwest, and even on early flights used the same "Long Legs And Short Nights" theme for stewardesses on board typical Southwest Airlines flights. In early 1971, Air Southwest changed its name to Southwest Airlines, and the first flight was on June 18, 1971. Its first flights were from Love Field in Dallas to Houston and San Antonio,[9] short hops with no-frills service and a simple fare structure, features that became the basis for Southwest's popularity and rapid growth in the coming years. The rest of 1971 and 1972 saw operating losses. One of the four aircraft was sold to Frontier Airlines and the proceeds used to make payroll and cover other expenses. Southwest continued to operate a schedule predicated on four aircraft but using only three, and in so doing the "ten minute turn" was born, and was the standard ground time for many years.[10] Southwest turned its first annual profit in 1973, and has done so every year since — a record unmatched by any other commercial airline.[11] Southwest has used financial techniques such as fuel hedging to bolster its profitability and counteract many of the fiscal disadvantages of operating an airline. To lock in the low historical prices Southwest believed were occurring at that time, Southwest used a mixture of swaps and call options to secure fuel in future years while paying prices they believed were low. The company also stated that with this new strategy, it faced substantial risks if the oil prices continued to go down, but they did not. Previously, Southwest had been more interested in reducing volatility of oil prices. Now, they hoped to reap large gains from oil price appreciation. According an annual report, here is the company's fuel hedge for forward years ("approximate" per barrel basis, as of mid-January): 2007 is 95% hedged at $50/barrel; 2008 is 65% hedged at $49/barrel; 2009 is over 50% hedged at $51/barrel; 2010 is over 25% hedged at $63/barrel; 2011 is over is 15% hedged at $64/barrel; 2012 is 15% hedged at $63/barrel. These are well below market rates, which Southwest factors into its low operating costs. However, this below-market oil cost will not continue forever; executives have said that Southwest faces increased exposure to the raw oil market every year. This is not a good sign for the airline, which is also facing tough competition from US legacy carriers that have lowered costs through bankruptcy. Southwest CEO Gary Kelly has decided to slow the airlines' growth as a response to this cost. At present, Southwest has enjoyed much positive press (and a strong financial boost) from its energy trading skills. However, while most analysts agree that volatility hedges can be beneficial, speculative hedges are not widely supported as a continuing strategy for profits. The early 2000s hedges may in retrospect be an anomalous, lucky event and also a claim to fame for Southwest Airlines' reputation as a financially adept company. When airline deregulation came in 1978, Southwest began planning to offer interstate service from Love Field. This caused a number of interest groups affiliated with Dallas-Ft. Worth Airport, including the city of Fort Worth, to push the Wright Amendment through Congress to restrict such flights.[17] Under the restrictions of the amendment, Southwest, and all other airlines, were barred from operating, or even ticketing passengers on flights from Love Field to destinations beyond the states immediately surrounding Texas. In effect, to travel through Love Field, a passenger and luggage would have to deplane and fly on a separate ticket, on a separate aircraft. The Wright Amendment's restrictions didn't apply to aircraft configured with 56 or fewer seats. In 2000, Legend Airlines attempted to operate long distance business-class flights using older DC-9s with 56 seats, but did not have the resources to survive American's legal and marketing attacks, and quickly ceased operations. Southwest has not used the 56 seat loophole, even with its market strength at Love Field and the availability of more modern regional jets such as the CRJ-700/900 and the Embraer ERJ 145 family. In 1997, Southwest's effort began to pay off with the Shelby Amendment, which added the states of Alabama, Mississippi, and Kansas to the list of permissible destination states. Southwest now offers service between Dallas Love Field and Jackson, MS, via a connection at Houston, which it couldn't do prior to the enactment of the Shelby Amendment. Since late 2004, Southwest has actively sought the full repeal of the Wright Amendment restrictions. In late 2005, Missouri was added to the list of permissible destination states via a transportation appropriations bill. New service from Love Field to St. Louis and Kansas City quickly started in December 2005. Southwest started selling tickets under the new law on October 19, 2006. Highlights of the agreement are the immediate elimination of through-ticketing prohibitions, and unrestricted flights to domestic destinations eight years after the legislation takes effect. This agreement was a resounding victory for Southwest Airlines because nationwide service became possible, and the law defined the maximum number of gates at Love Field. Southwest controls all of the Love Field gates except for the two each that American and Continental control. The future of the Legend Airlines terminal for use by commercial airlines is in doubt because of the limit on number of gates. Despite the restrictions on its home base, Southwest proceeded to build a successful business on an unusual model: flying multiple short, quick trips into the secondary (more efficient and less costly) airports of major cities, using primarily only one aircraft type, the Boeing 737. As part of its effort to control costs, Southwest tries to use secondary airports which generally have lower costs and may, or may not be, more convenient to travelers than the major airports to the same destinations. For example, Southwest flies to Midway Airport in Chicago, Fort Lauderdale-Hollywood International Airport and West Palm Beach in South Florida, Love Field in Dallas, Hobby Airport in Houston, Manchester-Boston Regional Airport in Manchester, New Hampshire, and T. F. Green Airport in Providence, Rhode Island, instead of O'Hare International Airport, Miami International Airport, DFW International, IAH Intercontinental in Houston, and Logan International Airport in Boston, respectively. Southwest also serves the New York Metropolitan area at Long Island MacArthur Airport. Southwest makes exceptions to the philosophy of serving secondary airports by flying into some larger airports in major cities, such as Phoenix Sky Harbor International Airport, Orlando International Airport, Detroit Metropolitan Airport, Philadelphia International, Denver International Airport, Cleveland Hopkins International Airport, Seattle-Tacoma International and Pittsburgh International. In the Baltimore-Washington market, Southwest has limited flights into one major airport (Washington Dulles International Airport) while maintaining their east-coast focus city at the region's other major airport, Baltimore-Washington International Airport. In the Los Angeles market Southwest flies to both the major city airport, Los Angeles International (LAX), and to three of the four secondary airports, Burbank-Bob Hope Airport, John Wayne Airport, and LA/Ontario International Airport (it does not serve Long Beach Airport). With the restoration of service out of San Francisco International Airport on August 26, 2007, Southwest now serves all three airports in the San Francisco Bay Area; the other two being Oakland International Airport and San Jose International Airport. On February 9, 2007, Southwest Airlines announced internally that it was planning to restart operations at San Francisco International Airport, a station the airline closed in 2001.[25] Southwest CEO Gary Kelly has stated that the airline plans to commence service at SFO beginning in the "early fall" of 2007. On May 11, 2007, in an e-mail to Rapid Rewards members, Southwest announced that service to and from San Francisco would begin August 26th with eight daily nonstops to San Diego, seven to Las Vegas and three to Chicago's Midway Airport. The success and profitability of Southwest's business model led to a common trend being named after the company: The Southwest Effect. Since Southwest's original mission in Texas was to make it less expensive than driving between two points (in the early 1970s, during the first major energy cost crisis in the U.S.), it developed a template for entering markets at rates that allowed the airline to be profitable, yet only on the basis of lean operations and high aircraft use. The key concept to the Southwest Effect is that when a low-fare carrier (or any aggressive and innovative company) enters a market, the market itself changes, and usually grows dramatically. For example, when fares drop by 50% from their historical averages, the number of new customers in that market may not just double, but actually quadruple, or more. Southwest has been a major inspiration to other low-cost airlines, and its business model has been repeated many times around the world. Europe's easyJet and Ryanair as well as Canada's WestJet, are some of the best known airlines to follow Southwest's business strategy in that continent (though easyJet operates two different aircraft models today). Other airlines with a business model based on Southwest's system include New Zealand's Freedom Air, Malaysia's AirAsia (the first and biggest LCC in Asia), Qantas's Jetstar (although Jetstar now operates two aircraft types) and Thailand's Nok Air. Southwest Airlines has mostly pursued a strategy of internal growth, rather than by acquisition of other airlines as commonly occurs. However, in addition to acquisition of Morris Air Transport (see above), Southwest did acquire competitor Muse Air in 1985, which operated McDonnell Douglas MD-80s. Muse Air was renamed TranStar Airlines. ATA Airlines, one of Southwest Airlines' main competitors in the Chicago market, historically operated out of Midway Airport alongside Southwest. ATA declared bankruptcy, and in 2004, Southwest injected capital into ATA that (among other things) would have resulted in Southwest's 27.5% ownership stake in ATA upon their exit from Chapter 11 bankruptcy proceedings. In late 2005, ATA secured $100 million in additional financing from the firm of Matlin Patterson, and Southwest's original deal with ATA was modified such that Southwest no longer retained the 27.5% stake (or any other financial interest) in ATA. The codeshare arrangement, however, continues to remain in place and has expanded, with some internal controversy, to include all of ATA's 17 destinations and all of Southwest's 63 destinations. In 2006, Southwest's pilot union approved a codeshare sideletter to their contract with limitations on the growth of this and other codeshare agreements. While these restrictions today are minor, outsourcing remains a growing concern in the unions current contract negotiations. During 2006, Southwest Airlines began marketing ATA only flights. ATA's dependence on the Southwest network continued to grow in 2006, and today ATA offers over 70 flights a week to Hawaii from Southwest's hubs in PHX, LAS, LAX, and OAK. Additional connecting service is available to many other cities across the United States. Plans have been announced for ATA to offer exclusive international service for Southwest by 2010. Southwest today has taken over all ground operations for ATA at MDW, OAK, PHX, LAX, and LAS. These contracts provide that Southwest ramp personnel will now handle all ground operations (loading of aircraft, ground servicing, etc.) for ATA. The details of these contracts have not been made public but represent Southwest's and ATA's growing mutually beneficial codeshare relationship. Presently, there is no plan to open the ATA/Southwest codeshare to ATA's sister carriers; North American Airlines or World Airways, even though they are co-owned by the same corporate entity created from ATA Holdings. On November 8, 2007, Global Aero Logistics, parent company of ATA, formally announced to Southwest Airlines that its code-share passengers would be flying upon North American Airlines crewed aircraft for a portion of the 2007 Christmas season. Beginning in February 2005, ATA was run by John Denison, Southwest's former Chief Financial Officer. Effective January 1, 2007, Denison turned things over to Subodh Karnik, who is now President and Chief Executive Officer. Denison remains ATA's Chairman and Chairman of Global Aero Logistics Inc., the new name of ATA Holdings. Tickets cannot be purchased through common online venues like Orbitz or Travelocity; a minority are booked through travel agents. Most of Southwest's tickets are issued directly by the airline over the phone or online at the company's website which features Web-only fare discounts. Unlike other major airlines, Southwest allows passengers to change reservations without additional cost. While this provides flexibility to customers, Southwest does not allow same-day standby travel on a different flight (usually a free service at other airlines) without upgrading to maximum fare. Customers are not assigned seats; rather, they are assigned to one of three "boarding groups" depending on their check-in time (earlier check-ins get to board earlier), and are left to choose their own seats on the plane, which helps the airline to board passengers faster. At the May 2006 shareholders meeting, Southwest management announced a study of potentially adopting an assigned-seating system in 2008, as part of a reservations-technology overhaul now under way. As of November 8, 2007 Southwest has implemented an update to their Boarding Procedure in which passengers are now assigned their Boarding letter (A, B or C) along with a number which provides them a specific place in line (Example: A32). The idea behind this is to allow customers to not have to wait in line and spend their time relaxing or catching up on work. They have also introduced Business Select fares, which adds a guaranteed "A" group boarding pass, extra Rapid Rewards credit, and a drink. As a result of the boarding policy, several independent companies have offered automatic check-in services for Southwest. These companies take customer's orders for check-in ahead of the 24 hour mark (when the airline makes a flight available for online check-in) and transmit the necessary data for check-in to Southwest as soon as the airline opens up online check-in for a particular flight. The result of this service is that people using it generally get the first boarding group (known as the "A" boarding group). These early check-in sites include Seat-Sniper.com and CheckinSooner.com. Southwest has not embraced this practice and in fact sued one company (boardfirst.com) in federal district court in Dallas for impermissible commercial use of its website and succeeded in getting the company shut down in October 2007. Southwest maintained excellent customer satisfaction ratings; in 2006, according to the Department of Transportation December year end operating statistics, Southwest ranked number one (lowest number of complaints) of all U.S. airlines for customer complaints, with 0.18 per 100,000 customers enplaned. Southwest Airlines has consistently received the fewest ratio of complaints per passengers boarded of all major U.S. carriers that have been reporting statistics to the Department of Transportation (DOT) since September 1987, which is when the DOT began tracking Customer Satisfaction statistics and publishing its Air Travel Consumer Report. In February 2006, Southwest instituted capacity controls to redeeming its free tickets. This means that the airline limits the seats offered to frequent travelers using free certificates on each flight, whereas previously if there was a seat available, one could use the award, provided the passenger was not flying on one of the five blackout dates. In early 2006, Southwest expanded its codeshare agreement with ATA Airlines and now allows redemption of award tickets on Hawaii flights at the rate of two awards per round trip flight. Southwest and ATA stress that reward availability to Hawaii will be very limited. Travelers can also earn twice the normal number of credits when they purchase airfare on Hawaii-bound flights. Instead of a lawsuit, the CEOs for both companies staged an arm wrestling match. Held at the now demolished Dallas Sportatorium (the famed wrestling facility) and set for two out of three rounds, the loser of each round was to pay $5,000 to the charity of their choice, with the winner gaining the use of the trademarked phrase. A promotional video was created showing the CEOs "training" for the bout (with CEO Herb Kelleher being helped up during a sit up where a cigarette and glass of whiskey (Wild Turkey 101) was waiting) and distributed among the employees and as a video press release along with the video of the match itself. Herb Kelleher lost the match for Southwest, with Stevens Aviation winning the rights to the phrase. Kurt Herwald, CEO of Stevens Aviation, immediately granted the use of "Just Plane Smart" to Southwest Airlines. The net result was both companies having use of the trademark, $15,000 going to charity and a healthy dose of goodwill publicity for both companies. The President of Southwest is Colleen Barrett, who has been with the company since day one. Southwest's CFO is Laura Wright. In July 2007, it was announced that Herb Kelleher will resign his position as Chairman effective May 2008. Colleen Barrett will leave her post on the Board of Directors and Corporate Secretary in May 2008 and President in July 2008. Both will remain active employees of Southwest Airlines. The American version of the reality show Airline showcased Southwest Airlines passengers and employees in daily mishaps and life at some of Southwest's major airports (BWI, MDW, LAX, & HOU). The show premiered January 5, 2004 on the A&E Network, but was canceled after 70 episodes on December 15, 2005. Southwest is the world's largest operator of the 737. Their current active fleet is over 500 aircraft. In terms of total 737 production (all models in history), deliveries of new aircraft from Boeing to Southwest accounts for approximately 9% of total production. Southwest has one of the largest fleets in North America. Southwest's original primary livery was beige and red, with orange on the tail end, and pinstripes of white separating each section of color. The word Southwest appears in white on the beige portion of the tail. (Although, on the original three 737-200s, from June of 1971, on the left side of the plane, the word Southwest was placed along the upper rear portion of the fuselage, with the word Airlines painted on the tail where Southwest is today N21SW. On the right side, the word Southwest was in the same place as today, but also had the word Airlines painted on the upper rear portion of the fuselage.N20SW. Southwest introduced the Canyon Blue Fleet in 2001, its first primary livery change in its 30-year history. Spirit One was the first plane painted in the color scheme. The new livery replaces the primary beige color with canyon blue and changes the Southwest text and pinstripes to gold. The pinstripe along the plane is drawn in a more curved pattern instead of the straight horizontal line separating the colors in the original. The original livery is gradually being phased out, but three aircraft will remain in the original livery to commemorate Southwest's original three cities. As of November 16, 2007, Southwest has nearly completed updating the fleet.[16] The first aircraft to be painted in the "Shamu" scheme was N334SW (1988), a 737-300, and it was later followed by N507SW (Shamu II) and N501SW (Shamu III), both 737-500s. Subsequent to the retirement of Southwest's 737-200s, the 737-500s began to stay within a smaller geographic area formerly operated by the 737-200s, and as such, Sea World was no longer getting the optimal national exposure from these two aircraft. Two 737-700 aircraft, N713SW and N715SW, were repainted as the new Shamu aircraft, and both N501SW and N507SW were eventually repainted in Canyon Blue colors. All three current Shamu aircraft are no longer referred to as Shamu I, II, or III. The artwork on the nose of each aircraft simply states "Shamu". The overhead bins of these aircraft display ads for Sea World, except towards the front and back of the airplane, where the bins get smaller and are no longer uniform. The first aircraft to be painted in the "Shamu" scheme was N334SW (1988), a 737-300, and it was later followed by N507SW (Shamu II) and N501SW (Shamu III), both 737-500s. Subsequent to the retirement of Southwest's 737-200s, the 737-500s began to stay within a smaller geographic area formerly operated by the 737-200s, and as such, Sea World was no longer getting the optimal national exposure from these two aircraft. Two 737-700 aircraft, N713SW and N715SW, were repainted as the new Shamu aircraft, and both N501SW and N507SW were eventually repainted in Canyon Blue colors. All three current Shamu aircraft are no longer referred to as Shamu I, II, or III. The artwork on the nose of each aircraft simply states "Shamu". The overhead bins of these aircraft display ads for Sea World, except towards the front and back of the airplane, where the bins get smaller and are no longer uniform. Triple Crown One: (1997) Livery dedicated to the employees of Southwest, in recognition of Southwest receiving five Triple Crown airline industry awards (best on-time record, best baggage handling, and fewest customer complaints). The overhead bins in Triple Crown One one are inscribed with the names of all employees that worked for Southwest at the time, in honor of their part in winning the award.(N647SW) Southwest received both the 5,000th 737 produced (February 13, 2006) (N230WN) and the 2,000th "Next Generation" 737 produced (July 27, 2006) (N248WN). The 2,000th "Next Generation" 737 is marked as such in its livery, though the 5,000th 737 is not similarly marked. All special planes prior to Spirit One originally wore the standard beige, red and orange livery colors on the vertical stabilizer and rudder. Subsequent special editions—Maryland One and Slam Dunk One, so far—feature tails with the canyon blue color scheme, and all earlier specials, with the exception of Triple Crown One have been repainted to match. On December 8, 2005, Southwest Airlines Flight 1248 skidded off a runway upon landing at Chicago Midway International Airport in heavy snow conditions. A six-year old boy died in a car struck by the plane after the plane skidded into a street. Passengers on board the aircraft and on the ground reported several minor injuries. The aircraft involved, N471WN, became N286WN after repairs. For 2007, the eighth year in a row, Business Ethics magazine lists Southwest Airlines in its “100 Best Corporate Citizens,” a list that ranks public companies based on their corporate service to various stakeholder groups. Southwest is one of only 11 repeat winners that have made the list all eight years According to Institutional Investor magazine, Southwest Airlines ranked number one in the Consumer category among all airlines as the “Most Shareholder Friendly Company” based on the effectiveness of Southwest’s governance and investor relations as part of their overall efforts to maximize share holder value. ABX Air�• Alaska Airlines�• Aloha Airlines�• American Airlines�• Astar Air Cargo�• ATA Airlines�• Atlas Air�• Continental Airlines�• Delta�Air�Lines�• Evergreen�International�Airlines�• FedEx Express�• Hawaiian Airlines�• JetBlue Airways�• Midwest Airlines�• Northwest�Airlines�• Southwest Airlines�• United Airlines�• UPS Airlines�• US Airways Associate Members: Aeroméxico�• Air Canada�• Air Jamaica�• Mexicana
The telephone is a telecommunications device that is used to transmit and receive sound (most commonly speech), usually two people conversing but occasionally three or more. It is one of the most common household appliances in the world today. Most telephones operate through transmission of electric signals over a complex telephone network which allows almost any phone user to communicate with almost anyone. The telephone handles two types of information: signals and voice, at different times on the same twisted pair of wires. The signaling equipment consists of a bell to alert the user of incoming calls, and a dial to enter the phone number for outgoing calls. A calling party wishing to speak to another telephone will pick up the handset, thus operating the switch hook, which puts the telephone into active state or off hook with a resistance short across the wires, causing current to flow. The telephone exchange detects the DC current, attaches a digit receiver, and sends dial tone to indicate readiness. The user pushes the number buttons, which are connected to a tone generator inside the dial, which generates DTMF tones. The exchange connects the line to the desired line and alerts that line. When a phone is inactive (on hook), its bell, beeper, flasher or other alerting device is connected across the line through a capacitor. The inactive phone does not short the line, thus the exchange knows it is on hook and only the bell is electrically connected. When someone calls this phone, the telephone exchange applies a high voltage pulsating signal, which causes the sound mechanism to ring, beep or otherwise alert the called party. When that user picks up the handset, the switchhook disconnects the bell, connects the voice parts of the telephone, and puts a resistance short on the line, confirming that the phone has been answered and is active. Both lines being off hook, the signaling job is complete. The parties are connected together and may converse using the voice parts of their telephones. The voice parts of the telephone are in the handset, and consist of a transmitter (often called microphone) and a receiver. The transmitter, powered from the line, puts out an electric current which varies in response to the acoustic pressure waves produced by the voice. The resulting variations in electric current are transmitted along the telephone line to the other phone, where they are fed into the coil of the receiver, which is a miniature loudspeaker. The varying electric current in the coil causes it to move back and forth, reproducing the acoustic pressure waves of the transmitter. When a party "hangs up" (puts the handset on the cradle), DC current ceases to flow in that line, thus signaling to the exchange switch to disconnect the telephone call. Credit for inventing the electric telephone remains in dispute. As with other great inventions such as radio, television, light bulb, and computer, there were several inventors who did pioneer experimental work on voice transmission over a wire and improved on each other's ideas. Antonio Meucci, Johann Philipp Reis, Elisha Gray, Alexander Graham Bell, and Thomas Edison, among others, have all been credited with pioneer work on the telephone. The early history of the telephone is a confusing morass of claim and counterclaim, which was not clarified by the huge mass of lawsuits which hoped to resolve the patent claims of individuals. The Bell and Edison patents, however, were forensically victorious and commercially decisive. 7 March 1876—Bell's U.S. patent 174,465 "Improvement in Telegraphy" is granted, covering "the method of, and apparatus for, transmitting vocal or other sounds telegraphically … by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sound." 27 April 1877—Edison files for a patent on a carbon (graphite) transmitter. The patent 474,230 was granted 3 May 1892, after a 15 year delay because of litigation. Edison was granted patent 222,390 for a carbon granules transmitter in 1879. Early telephones were technically diverse. Some used a liquid transmitter, some had a metal diaphragm that induced current in an electromagnet wound around a permanent magnet, and some were "dynamic" - their diaphragm vibrated a coil of wire in the field of a permanent magnet or the coil vibrated the diaphragm. This dynamic kind survived in small numbers through the 20th century in military and maritime applications where its ability to create its own electrical power was crucial. Most, however, used the Edison/Berliner carbon transmitter, which was much louder than the other kinds, even though it required an induction coil, actually acting as an impedance matching transformer to make it compatible to the impedance of the line. The Edison patents kept the Bell monopoly viable into the 20th century, by which time the network was more important than the instrument. Early telephones were locally powered, using a dynamic transmitter or else powering the transmitter with a local battery. One of the jobs of outside plant personnel was to visit each telephone periodically to inspect the battery. During the 20th century, "common battery" operation came to dominate, powered by "talk battery" from the telephone exchange over the same wires that carried the voice signals. Late in the century, wireless handsets brought a revival of local battery power. Early telephones had one wire for both transmitting and receiving of audio, with ground return as used in telegraphs. The earliest dynamic telephones also had only one opening for sound, and the user alternately listened and spoke (rather, shouted) into the same hole. Sometimes the instruments were operated in pairs at each end, making conversation more convenient but were more expensive. At first, the benefits of an exchange were not exploited. Telephones instead were leased in pairs to the subscriber, who had to arrange telegraph contractors to construct a line between them, for example between his home and his shop. Users who wanted the ability to speak to several different locations would need to obtain and set up three or four pairs of telephones. Western Union, already using telegraph exchanges, quickly extended the principle to its telephones in New York City and San Francisco, and Bell was not slow in appreciating the potential. Signalling began in an appropriately primitive manner. The user alerted the other end, or the exchange operator, by whistling into the transmitter. Exchange operation soon resulted in telephones being equipped with a bell, first operated over a second wire and later with the same wire using a condenser. Telephones connected to the earliest Strowger automatic exchanges had seven wires, one for the knife switch, one for each telegraph key, one for the bell, one for the push button and two for speaking. Rural and other telephones that were not on a common battery exchange had a "magneto" or hand cranked generator to produce a high voltage alternating signal to ring the bells of other telephones on the line and to alert the operator. In the 1890s a new smaller style of telephone was introduced, packaged in three parts. The transmitter stood on a stand, known as a "candlestick" for its shape. When not in use, the receiver hung on a hook with a switch in it, known as a "switchhook." Previous telephones required the user to operate a separate switch to connect either the voice or the bell. With the new kind, the user was less likely to leave the phone "off the hook". In phones connected to magneto exchanges, the bell, induction coil, battery and magneto were in a separate "bell box." In phones connected to common battery exchanges, the bell box was installed under a desk, or other out of the way place, since it did not need a battery or magneto. Disadvantages of single wire operation such as crosstalk and hum from nearby AC power wires had already led to the use of twisted pairs and, for long distance telephones, four-wire circuits. Users at the beginning of the 20th century did not place long distance calls from their own telephones but made an appointment to use a special sound proofed long distance telephone booth furnished with the latest technology. What turned out to be the most popular and longest lasting physical style of telephone was introduced in the early 20th century, including Bell's Model 102. A carbon granule transmitter and electromagnetic receiver were united in a single molded plastic handle, which when not in use sat in a cradle in the base unit. The circuit diagram of the Model 102 shows the direct connection of the receiver to the line, while the transmitter was induction coupled, with energy supplied by a local battery. The coupling transformer, battery, and ringer were in a separate enclosure. The dial switch in the base interrupted the line current by repeatedly but very briefly disconnecting the line 1-10 times for each digit, and the hook switch (in the center of the circuit diagram) permanently disconnected the line and the transmitter battery while the handset was on the cradle. After the 1930s, the base also enclosed the bell and induction coil, obviating the old separate bell box. Power was supplied to each subscriber line by central office batteries instead of a local battery, which required periodic service. For the next half century, the network behind the telephone became progressively larger and much more efficient, but after the dial was added the instrument itself changed little until touch tone replaced the dial in the 1960s. The Public Switched Telephone Network (PSTN) has gradually evolved towards digital telephony which has improved the capacity and quality of the network. End-to-end analog telephone networks were first modified in the early 1960s by upgrading transmission networks with T1 carrier systems. Later technologies such as SONET and fiber optic transmission methods further advanced digital transmission. Although analog carrier systems existed, digital transmission made it possible to significantly increase the number of channels multiplexed on a single transmission medium. While today the end instrument remains analog, the analog signals reaching the aggregation point (Serving Area Interface (SAI) or the central office (CO) ) are typically converted to digital signals. Digital loop carriers (DLC) are often used, placing the digital network ever closer to the customer premises, relegating the analog local loop to legacy status. Internet Protocol (IP) telephony (also known as Internet telephony) is a service based on Voice over IP (VoIP), a disruptive technology that is rapidly gaining ground against traditional telephone network technologies. In Japan and South Korea up to 10% of subscribers, as of January 2005, have switched to this digital telephone service. A January 2005 Newsweek article suggested that Internet telephony may be "the next big thing." [1] As of 2006 many VoIP companies offer service to consumers and businesses. IP telephony uses a broadband Internet connection and IP Phones to transmit conversations as data packets. In addition to replacing POTS(plain old telephone service), IP telephony is also competing with mobile phone networks by offering free or lower cost connections via WiFi hotspots. VoIP is also used on private wireless networks which may or may not have a connection to the outside telephone network. IP telephony technology transforms many non-telephone electronics devices into unified communications devices which simulate telephone usage, such as adding telephone-like features to portable game devices, digital picture frames, or handheld GPS receivers, typically by incorporating a voice engine. When used on a personal computer, an IP telephone is referred to as a soft phone. In some countries, many telephone operating companies (commonly abbreviated to telco in American English) are in competition to provide telephone services. Some of them are included in the following list. However, the list only includes facilities based providers and not companies which lease services from facilities based providers in order to serve their customers.
A number is an abstract idea used in counting and measuring. A symbol which represents a number is called a numeral, but in common usage the word number is used for both the idea and the symbol. In addition to their use in counting and measuring, numerals are often used for labels (telephone numbers), for ordering (serial numbers), and for codes (ISBNs). In mathematics, the definition of number has been extended over the years to include such numbers as zero, negative numbers, rational numbers, irrational numbers, and complex numbers. In the base ten number system, in almost universal use today, the symbols for natural numbers are written using ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. In this base ten system, the rightmost digit of a natural number has a place value of one, and every other digit has a place value ten times that of the place value of the digit to its right. The symbol for the set of all natural numbers is N, also written . Negative numbers are numbers that are less than zero. They are the opposite of positive numbers. For example, if a positive number indicates a bank deposit, then a negative number indicates a withdrawal of the same amount. Negative numbers are usually written by writing a negative sign in front of the number they are the opposite of. Thus the opposite of 7 is written −7. When the set of the opposites of the natural numbers is combined with the natural numbers and zero, one obtains the integers Z (German Zahl, plural Zahlen), also written . If the absolute value of m is greater than n, then the absolute value of the fraction is greater than 1. Fractions can be greater than, less than, or equal to 1 and can also be positive, negative, or zero. The set of all fractions includes the integers, since every integer can be written as a fraction with denominator 1. For example −7 can be written −7/1. The symbol for the rational numbers is Q (for quotient), also written . The real numbers include all of the measuring numbers. Real numbers are usually written using decimal numerals, in which a decimal point is placed to the right of the digit with place value one. Following the decimal point, each digit has a place value one-tenth the place value of the digit to its left. Thus represents 1 hundred, 2 tens, 3 ones, 4 tenths, 5 hundredths, and 6 thousandths. In saying the number, the decimal is read "point", thus: "one two three point four five six". In, for example, the US and UK, the decimal is represented by a period, in continental Europe by a comma. Zero is often written as 0.0 and negative real numbers are written with a preceding minus sign: Moving to a greater level of abstraction, the real numbers can be extended to the complex numbers. This set of numbers arose, historically, from the question of whether a negative number can have a square root. This led to the invention of a new number: the square root of negative one, denoted by i, a symbol assigned by Leonhard Euler, and called the imaginary unit. The complex numbers consist of all numbers of the form where a and b are real numbers. In the expression a + bi, the real number a is called the real part and bi is called the imaginary part. If the real part of a complex number is zero, then the number is called an imaginary number or is referred to as purely imaginary; if the imaginary part is zero, then the number is a real number. Thus the real numbers are a subset of the complex numbers. If the real and imaginary parts of a complex number are both integers, then the number is called a Gaussian integer. The symbol for the complex numbers is C or . In abstract algebra, the complex numbers are an example of an algebraically closed field, meaning that every polynomial with complex coefficients can be factored into linear factors. Like the real number system, the complex number system is a field and is complete, but unlike the real numbers it is not ordered. That is, there is no meaning in saying that i is greater than 1, nor is there any meaning in saying that that i is less than 1. In technical terms, the complex numbers lack the trichotomy property. The idea behind p-adic numbers is this: While real numbers may have infinitely long expansions to the right of the decimal point, these numbers allow for infinitely long expansions to the left. The number system which results depends on what base is used for the digits: any base is possible, but a system with the best mathematical properties is obtained when the base is a prime number. For dealing with infinite collections, the natural numbers have been generalized to the ordinal numbers and to the cardinal numbers. The former gives the ordering of the collection, while the latter gives its size. For the finite set, the ordinal and cardinal numbers are equivalent, but they differ in the infinite case. Sets of numbers that are not subsets of the complex numbers are sometimes called hypercomplex numbers. They include the quaternions H, invented by Sir William Rowan Hamilton, in which multiplication is not commutative, and the octonions, in which multiplication is not associative. Elements of function fields of non-zero characteristic behave in some ways like numbers and are often regarded as numbers by number theorists. Numbers should be distinguished from numerals, the symbols used to represent numbers. The number five can be represented by both the base ten numeral '5' and by the Roman numeral 'V'. Notations used to represent numbers are discussed in the article numeral systems. An important development in the history of numerals was the development of a positional system, like modern decimals, which can represent very large numbers. The Roman numerals require extra symbols for larger numbers. It is speculated that the first known use of numbers dates back to around 30000 BC, bones or other artifacts have been discovered with marks cut into them which are often considered tally marks. The use of these tally marks have been suggested to be anything from counting elapsed time, such as numbers of days, or keeping records of amounts. Tallying systems have no concept of place-value (such as in the currently used decimal notation), which limit its representation of large numbers and as such is often considered that this is the first kind of abstract system that would be used, and could be considered a Numeral System. The use of zero as a number should be distinguished from its use as a placeholder numeral in place-value systems. Many ancient Indian texts use a Sanskrit word Shunya to refer to the concept of void; in mathematics texts this word would often be used to refer to the number zero. [2]. In a similar vein, Pāṇini (5th century BC) used the null (zero) operator (ie a lambda production) in the Ashtadhyayi, his algebraic grammar for the Sanskrit language. (also see Pingala) Records show that the Ancient Greeks seemed unsure about the status of zero as a number: they asked themselves "how can 'nothing' be something?" leading to interesting philosophical and, by the Medieval period, religious arguments about the nature and existence of zero and the vacuum. The paradoxes of Zeno of Elea depend in large part on the uncertain interpretation of zero. (The ancient Greeks even questioned if 1 was a number.) The late Olmec people of south-central Mexico began to use a true zero (a shell glyph) in the New World possibly by the 4th century BC but certainly by 40 BC, which became an integral part of Maya numerals and the Maya calendar, but did not influence Old World numeral systems. By 130, Ptolemy, influenced by Hipparchus and the Babylonians, was using a symbol for zero (a small circle with a long overbar) within a sexagesimal numeral system otherwise using alphabetic Greek numerals. Because it was used alone, not as just a placeholder, this Hellenistic zero was the first documented use of a true zero in the Old World. In later Byzantine manuscripts of his Syntaxis Mathematica (Almagest), the Hellenistic zero had morphed into the Greek letter omicron (otherwise meaning 70). Another true zero was used in tables alongside Roman numerals by 525 (first known use by Dionysius Exiguus), but as a word, nulla meaning nothing, not as a symbol. When division produced zero as a remainder, nihil, also meaning nothing, was used. These medieval zeros were used by all future medieval computists (calculators of Easter). An isolated use of their initial, N, was used in a table of Roman numerals by Bede or a colleague about 725, a true zero symbol. An early documented use of the zero by Brahmagupta (in the Brahmasphutasiddhanta) dates to 628. He treated zero as a number and discussed operations involving it, including division. By this time (7th century) the concept had clearly reached Cambodia, and documentation shows the idea later spreading to China and the Islamic world. During the 600s, negative numbers were in use in India to represent debts. Diophantus’ previous reference was discussed more explicitly by Indian mathematician Brahmagupta, in Brahma-Sphuta-Siddhanta 628, who used negative numbers to produce the general form quadratic formula that remains in use today. However, in the 12th century in India, Bhaskara gives negative roots for quadratic equations but says the negative value "is in this case not to be taken, for it is inadequate; people do not approve of negative roots." It is likely that the concept of fractional numbers dates to prehistoric times. Even the Ancient Egyptians wrote math texts describing how to convert general fractions into their special notation. Classical Greek and Indian mathematicians made studies of the theory of rational numbers, as part of the general study of number theory. The best known of these is Euclid's Elements, dating to roughly 300 BC. Of the Indian texts, the most relevant is the Sthananga Sutra, which also covers number theory as part of a general study of mathematics. The concept of decimal fractions is closely linked with decimal place value notation; the two seem to have developed in tandem. For example, it is common for the Jain math sutras to include calculations of decimal-fraction approximations to pi or the square root of two. Similarly, Babylonian math texts had always used sexagesimal fractions with great frequency. The sixteenth century saw the final acceptance by Europeans of negative, integral and fractional numbers. The seventeenth century saw decimal fractions with the modern notation quite generally used by mathematicians. But it was not until the nineteenth century that the irrationals were separated into algebraic and transcendental parts, and a scientific study of theory of irrationals was taken once more. It had remained almost dormant since Euclid. The year 1872 saw the publication of the theories of Karl Weierstrass (by his pupil Kossak), Heine (Crelle, 74), Georg Cantor (Annalen, 5), and Richard Dedekind. Méray had taken in 1869 the same point of departure as Heine, but the theory is generally referred to the year 1872. Weierstrass's method has been completely set forth by Salvatore Pincherle (1880), and Dedekind's has received additional prominence through the author's later work (1888) and the recent endorsement by Paul Tannery (1894). Weierstrass, Cantor, and Heine base their theories on infinite series, while Dedekind founds his on the idea of a cut (Schnitt) in the system of real numbers, separating all rational numbers into two groups having certain characteristic properties. The subject has received later contributions at the hands of Weierstrass, Kronecker (Crelle, 101), and Méray. Continued fractions, closely related to irrational numbers (and due to Cataldi, 1613), received attention at the hands of Euler, and at the opening of the nineteenth century were brought into prominence through the writings of Joseph Louis Lagrange. Other noteworthy contributions have been made by Druckenmüller (1837), Kunze (1857), Lemke (1870), and Günther (1872). Ramus (1855) first connected the subject with determinants, resulting, with the subsequent contributions of Heine, Möbius, and Günther, in the theory of Kettenbruchdeterminanten. Dirichlet also added to the general theory, as have numerous contributors to the applications of the subject. The first results concerning transcendental numbers were Lambert's 1761 proof that π cannot be rational, and also that en is irrational if n is rational (unless n = 0). (The constant e was first referred to in Napier's 1618 work on logarithms.) Legendre extended this proof to showed that π is not the square root of a rational number. The search for roots of quintic and higher degree equations was an important development, the Abel–Ruffini theorem (Ruffini 1799, Abel 1824) showed that they could not be solved by radicals (formula involving only arithmetical operations and roots). Hence it was necessary to consider the wider set of algebraic numbers (all solutions to polynomial equations). Galois (1832) linked polynomial equations to group theory giving rise to the field of Galois theory. Even the set of algebraic numbers was not sufficient and the full set of real number includes transcendental numbers. The existence of which was first established by Liouville (1844, 1851). Hermite proved in 1873 that e is transcendental and Lindemann proved in 1882 that π is transcendental. Finally Cantor shows that the set of all real numbers is uncountably infinite but the set of all algebraic numbers is countably infinite, so there is an uncountably infinite number of transcendental numbers. The earliest known conception of mathematical infinity appears in the Yajur Veda, which at one point states "if you remove a part from infinity or add a part to infinity, still what remains is infinity". Infinity was a popular topic of philosophical study among the Jain mathematicians circa 400 BC. They distinguished between five types of infinity: infinite in one and two directions, infinite in area, infinite everywhere, and infinite perpetually. In the West, the traditional notion of mathematical infinity was defined by Aristotle, who distinguished between actual infinity and potential infinity; the general consensus being that only the latter had true value. Galileo's Two New Sciences discussed the idea of one-to-one correspondences between infinite sets. But the next major advance in the theory was made by Georg Cantor; in 1895 he published a book about his new set theory, introducing, among other things, the continuum hypothesis. A modern geometrical version of infinity is given by projective geometry, which introduces "ideal points at infinity," one for each spatial direction. Each family of parallel lines in a given direction is postulated to converge to the corresponding ideal point. This is closely related to the idea of vanishing points in perspective drawing. The earliest fleeting reference to square roots of negative numbers occurred in the work of the mathematician and inventor Heron of Alexandria in the 1st century AD, when he considered the volume of an impossible frustum of a pyramid. They became more prominent when in the 16th century closed formulas for the roots of third and fourth degree polynomials were discovered by Italian mathematicians (see Niccolo Fontana Tartaglia, Gerolamo Cardano). It was soon realized that these formulas, even if one was only interested in real solutions, sometimes required the manipulation of square roots of negative numbers. This was doubly unsettling since they did not even consider negative numbers to be on firm ground at the time. The term "imaginary" for these quantities was coined by René Descartes in 1637 and was meant to be derogatory (see imaginary number for a discussion of the "reality" of complex numbers). A further source of confusion was that the equation The existence of complex numbers was not completely accepted until the geometrical interpretation had been described by Caspar Wessel in 1799; it was rediscovered several years later and popularized by Carl Friedrich Gauss, and as a result the theory of complex numbers received a notable expansion. The idea of the graphic representation of complex numbers had appeared, however, as early as 1685, in Wallis's De Algebra tractatus. Also in 1799, Gauss provided the first generally accepted proof of the fundamental theorem of algebra, showing that every polynomial over the complex numbers has a full set of solutions in that realm. The general acceptance of the theory of complex numbers is not a little due to the labors of Augustin Louis Cauchy and Niels Henrik Abel, and especially the latter, who was the first to boldly use complex numbers with a success that is well known. Gauss studied complex numbers of the form a + bi, where a and b are integral, or rational (and i is one of the two roots of x2 + 1 = 0). His student, Ferdinand Eisenstein, studied the type a + bω, where ω is a complex root of x3 − 1 = 0. Other such classes (called cyclotomic fields) of complex numbers are derived from the roots of unity xk − 1 = 0 for higher values of k. This generalization is largely due to Ernst Kummer, who also invented ideal numbers, which were expressed as geometrical entities by Felix Klein in 1893. The general theory of fields was created by Évariste Galois, who studied the fields generated by the roots of any polynomial equation F(x) = 0. Prime numbers have been studied throughout recorded history. Euclid devoted one book of the Elements to the theory of primes; in it he proved the infinitude of the primes and the fundamental theorem of arithmetic, and presented the Euclidean algorithm for finding the greatest common divisor of two numbers. In 1796, Adrien-Marie Legendre conjectured the prime number theorem, describing the asymptotic distribution of primes. Other results concerning the distribution of the primes include Euler's proof that the sum of the reciprocals of the primes diverges, and the Goldbach conjecture which claims that any sufficiently large even number is the sum of two primes. Yet another conjecture related to the distribution of prime numbers is the Riemann hypothesis, formulated by Bernhard Riemann in 1859. The prime number theorem was finally proved by Jacques Hadamard and Charles de la Vallée-Poussin in 1896.
A number is an abstract idea used in the counting and measurement. A symbol that represents a number is called a numeral, but in the common use of the word number is used both for the idea and the symbol. In addition to their use in counting and measurement, numbers are often used to label (phone numbers), in order (serial numbers), and by codes (ISBNs). In mathematics, defining the number has been extended over the years to include such numbers as zero, negative numbers, rational numbers, irrational numbers and complex numbers. On the basis ten number system, in use today almost universal, the symbols for natural numbers are written using ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. On this basis ten system, the right digit of a natural number has a value of a place, and all other figures have a place ten times the value of the place value of the digit to the right. The symbol for the set of all natural numbers is N, also in writing. Negative numbers are numbers that are less than zero. They are the opposite of positive numbers. For example, if a positive number indicates a bank deposit, then a negative number indicates a withdrawal of the same amount. Negative numbers are usually written by writing a negative sign in front of the number they are the opposite of. Thus, the opposite of 7 is written -7. When the number of negative integers are combined with the positive whole numbers and zero, one gets the whole Z (German Zahl, Zahlen plural), also in writing. If the absolute value of m is greater than n, then the absolute value of the fraction is greater than 1. Fractions can be higher, lower or equal to 1 and also can be positive, negative or zero. The set of all fractions includes the whole, since every integer can be written as a fraction with denominator 1. For example -7 can be written -7 / 1. The symbol for rational numbers is Q (per ratio), also in writing. The real numbers include all issues of measurement. Real numbers are usually written using decimal numbers in a decimal point is placed on the right of the digit with a value spot. After the decimal point, each digit is a place value one tenth of the value of the site for the left digit. Thus, represents 1 hundred, 2 dozens, 3 ones, 4 tenths, 5 hundredths, thousandths and 6. In saying the number, the decimal is read "point", thus: "one point two three four five six". In, for example, the E.U. And the United Kingdom, the decimal is represented by a period in continental Europe by a comma. Zero is often written as 0.0 and negative real numbers are written with the first sign: Move to a higher level of abstraction, the real numbers can be extended to complex numbers. This set of figures emerged, historically, from the question of whether a negative number can be a square root. This led to the invention of a new issue: the square root of a negative, denoted by i, a symbol assigned by Leonhard Euler, and called for the imaginary unit. The figures complex consisting of all issues in the way Where a and b are real numbers. In the words + bi, the actual number is called the real part and b is called the imaginary part. If the real part of a complex number is zero, then the number is called an imaginary or is mentioned as purely imaginary; is the imaginary part is zero, then the number is a real number. Thus, the real numbers are a subset of complex numbers. If the real and imaginary parts of a complex number are both whole, then the number is called Gaussian integer. The symbol for the complex numbers is C or. In abstract algebra, complex numbers are an example of a field algebraically closed, which means that every polynomial coefficients with complex can be integrated into linear factors. Like the real number system, the number system is a complex area and is complete, but unlike the real numbers, is not ordained. That is, there is no sense in what I say is more than 1, nor is there any meaning in saying that i is less than 1. In technical terms, the numbers lack the complex trichotomy property. The idea behind p-add numbers is this: While actual numbers may have infinitely long expansions to the right of the decimal point, these numbers allow the infinitely long expansions to the left. The number system, which depends on results that base is used for the digits: any basis is possible, but a system with the best mathematical properties is obtained when the base is a prime number. To deal with infinite collections, the natural numbers were generalized ordinal numbers and the numbers for the Cardinals. The former gave the ordering of the collection, while the second gave his size. For all finite, the cardinal and ordinal numbers are equivalent, but differ in the case infinity. Sets of numbers that are not subsets of the complex numbers include quaternions H, invented by Sir William Rowan Hamilton, which is noncommutative multiplication, and octonions, in which multiplication is not associative. Elements of the function characteristic of finite fields behave, in some respects, such as numbers and are often regarded as serial numbers theoretical. Numbers must be distinguished from numbers, the symbols used to represent numbers. The number five can be represented by both the base in December numeral'5 'and the Roman numeral' V '. Ratings used to represent numbers are discussed in Article numeral systems. An important development in the history of numbering has been the development of a positional system, as the modern decimal, which can represent a large number. The Roman numerals require extra symbols for larger numbers. It is speculated that the first use of numbers known dates back to around 30000 BC, bones or other artifacts were discovered with cut marks where they are often considered registration marks. The use of these marks record were suggested to be something of counting time, such as numbers of days, or keep records of the amounts. Tallying systems have no concept of the place of value (as currently used in decimal notation), which limit its representation of a large number and, as such, is often considered that this is the first kind of abstract system that would be used, and could be Considered a system numbers. The use of zero as the number should be distinguished from its use as a placeholder numeral instead of value systems. Many ancient Indian texts using a Sanskrit word Shunya to refer to the concept of invalidity; in mathematics texts that word would often be used to refer to the number zero. [2]. Similarly, Pāṇini (5 th century BC) used the zero (zero) operator (ie a production lambda) in the Ashtadhyayi, algebraic their grammar for the language Sanskrit. (See also Pingala) records show that the ancient Greeks seemed unsure about the status of zero as a number: they asked themselves "how can" nothing "is a thing?" Taking interesting and philosophical, the medieval period, religious arguments about the nature and the existence of zero in the vacuum. The paradoxes of Zeno of Elea depend in large part on the interpretation of zero uncertain. (The ancient Greeks until 1 has been questioned whether a paragraph.) The late Olmec people of south-central Mexico began using a true zero (a shell glyph) in the New World possibly through the 4 th century BC, but certainly in 40 BC, which became an integral part of Maya numerals and the Maya calendar, but not influenced Old World numeral systems. By 130, Ptolemy, influenced by Hipparchus and the Babylonians, was using a symbol for zero (a small circle with a long overbar) within a system sexagesimal numeral one using alphabetical Greek numerals. Because it was used alone, not as just a space, this Hellenistic zero was the first documented use of a real zero in the Old World. In later Byzantine manuscripts of his Syntaxis Mathematica (Almagest), the Hellenistic zero had morphed the Greek letter omicron (another meaning 70). Another true zero was used in tables alongside Roman numerals by 525 (first use known as Dionysius Exiguus), but as a word, nulla meaning nothing, not as a symbol. When division produced zero as a remainder, nihil, also meaning nothing, was used. These medieval zeros were used by all future medieval computists (calculators of Easter). An isolated use of their initial, N, was used in a table of Roman numerals by Bede or a colleague about 725, a true zero symbol. One of the first documented use of zero by Brahmagupta (Brahmasphutasiddhanta) dates to 628. He treated zero as a number and discussed operations involving including division. At this time (7th century), the concept had clearly reached Cambodia, and documentation shows the idea later spreading to China and the Islamic world. During the 600s, negative numbers were in use in India to represent debts. Diophantus' reference has been discussed more explicitly by Indian mathematician Brahmagupta, in the Brahma-Sphuta-Siddhanta 628, which used to produce the negative numbers in general quadratic formula that remains in use today. However, the century 12 in India, Bhaskara gives negative roots of quadratic equations, but says that the negative value "is, in this case, not to be taken as it is inadequate; people do not approve of negative roots." It is likely that the concept of fractional numbers dates from pre-historic times. Even the ancient Egyptians wrote math texts describing how to convert fractions in particular its overall rating. Classic Greek and Indian studies made of the mathematical theory of rational numbers, as part of the global study of number theory. The best known is Euclid's Elements, which dates from about 300 BC. Do Indian texts, the most relevant is the Sthananga Sutra, which also covers number theory as part of a general study of mathematics. The concept of decimal fractions is closely related to the decimal value notation, the two seem to have developed in tandem. For example, it is common for mathematics Jain sutras to include calculations of approximations a decimal fraction-pi or the square root of two. Similarly, Babylonian mathematics texts had always used sexagesimal fractions with great frequency. In the sixteenth century, the acceptance by Europeans of negative final, integral and fractional numbers. XVII Century saw decimal fractions with the modern notation quite often used by mathematicians. But it was not until the nineteenth century that the irrationals have been split into algebraic and transcendental parts, and a scientific study of the theory of irrationals was taken once more. He had remained almost dormant since Euclid. The year 1872 saw the publication of the theories of Karl Weierstrass theorems (for his pupil Kossak), Heine (Crelle, 74), Georg Cantor (Annalen, 5), and Richard Dedekind. Méray had taken in 1869 the same point of departure as Heine, but the theory is generally refers to the year 1872. Weierstrass theorems of the method has been completely defined by Salvatore Pincherle (1880), and Dedekind's received more prominence through the work of the author, later (1888) and the recent approval by Paul Tannery (1894). Weierstrass theorems, Cantor, and Heine base their theories about infinite series, while his Dedekind found in the idea of a cut (Schnitt) in the system of real numbers, separating all rational numbers into two groups with some characteristic properties. The subject has received contributions later at the hands of Weierstrass theorems, Kronecker (Crelle, 101) and Méray. Fractions continuous, closely related to irrational numbers (and due to Cataldi, 1613), received attention at the hands of Euler, and the opening of the nineteenth century were brought to prominence through the writings of Joseph Louis Lagrange. Other notable contributions were made by Druckenmüller (1837), Kunze (1857), Lemke (1870), and Günther (1872). Ramus (1855) first connected with the theme determinants resulting, with the subsequent contributions of Heine, Möbius, and Günther, in the theory of Kettenbruchdeterminanten. Dirichlet also added to the general theory, as well as the many contributors to the applications of the subject. The first results relating transcendental numbers were Lambert's 1761 proves that π may not be rational, and that is irrational in if n is rational (unless n = 0). (A constant and was first mentioned in 1618 Napier's work on logarithms.) Legendre extended to this evidence showed that π is the square root of a rational number. The search for roots of quintic and greater degree equations has been an important development, the Abel-Ruffini theorem (Ruffini 1799, Abel 1824) showed that they could not be solved by radical (formula involving only the arithmetic operations and roots). Therefore, it was necessary to consider the wider set of algebraic numbers (all solutions of polynomial equations). Galois (1832) linked to the group polynomial equations theory that gave rise to the field of Galois theory. Even the set of algebraic numbers was not sufficient and complete the set of real numbers figure includes transcendental. The existence of which was first established by Liouville (1844, 1851). Hermite proved in 1873 and is transcendental and Lindemann proved in 1882 that π is transcendental. Finally Cantor shows that the set of all real numbers are uncountably infinite, but the set of all numbers is algebraic countably infinite, so there is an infinite number of uncountably transcendental numbers. The oldest known design of mathematical infinity appears in the Yajur Veda, which at one point states "if you remove a piece of infinity or add a part to infinity, what remains is infinite." Infinity has been a popular topic of study philosophical between the Jain mathematicians circa 400 BC. They distinguish between five types of infinity: infinite in one and two ways, in the infinite space, infinite everywhere, and infinite perpetually. In the West, the traditional concept of mathematical infinity was defined by Aristotle, which distinguish between real and infinite potential infinity, the general consensus that only the latter had real value. Galileo's Two New Sciences discussed the idea of one-to-one correspondence between sets infinite. But the next great breakthrough in the theory was done by Georg Cantor, in 1895 he published a book on his new set theory, introducing, among other things, the continuum hypothesis. A modern version of infinite geometrical is amended by projective geometry, which introduces "ideal points at infinity," one for each direction space. Each family of parallel lines in a certain direction is postulated to converge to the point corresponding ideal. This is closely related to the idea of escape points drawing in perspective. The first fleeting reference to the square roots of negative numbers occurred in the work of mathematician and inventor Heron of Alexandria in the 1 st century AD, when it considered the volume of an impossible frustum of a pyramid. They became more prominent when No 16 century closed formulas for the roots of the third and fourth degree polynomials were discovered by mathematical Italians (see Fontana Niccolo Tartaglia, Gerolamo Cardano). It was soon realized that these formulas, even when only one was interested in real solutions, sometimes required the manipulation of the square roots of negative numbers. This was doubly disturbing, since not even considered to be negative numbers on firm ground at the moment. The term "imaginary" for these quantities was coined by René Descartes by 1637 and was designed to be derogatory (see imaginary number for a discussion on the "reality" of complex numbers). Another source of confusion was that the equation the existence of complex numbers was not fully accepted until the geometrical interpretation had been described by Caspar Wessel in 1799, was rediscovered many years later and popularized by Carl Friedrich Gauss, and as a result the theory of Complex Numbers received a remarkable expansion. The idea of the graphical representation of complex numbers had appeared, however, once in 1685, in Wallis's De Algebra tractatus. Also in 1799, Gauss from the first generally accepted proof of the fundamental theorem of algebra, showing that every polynomial on the complex numbers has a complete set of solutions in this area. The general acceptance of the theory of complex numbers is not a little due to the work of Augustin Louis Cauchy and Niels Henrik Abel, and especially the latter, which was the first to use bravely complex numbers with a success that is well known. Gauss studied complex numbers of the form a + bi, where a and b are full, or rational (ei is one of the two roots of x2 + 1 = 0). His student, Ferdinand Eisenstein, studied the type ω a + b, where ω is a complex from scratch x3 - 1 = 0. Other these classes (called cyclotomic fields), complex numbers are derived from the root of the unit xk - 1 = 0 for higher values of k. This generalization is largely due to Ernst Kummer, who also invented ideal figures, which were expressed as geometric entities by Felix Klein, in 1893. The general theory of the fields was created by Évariste Galois, who studied the fields generated by the roots of any polynomial equation F (x) = 0. Prime numbers have been studied throughout recorded history. Euclides Elements of a book devoted to the theory of cousins, in which he revealed the infinitude of prime and fundamental theorem of arithmetic, and presented the Euclidean algorithm for finding the greatest common divisor of two numbers. In 1796, Adrien-Marie Legendre conjectured the prime number theorem, describing the asymptotic distribution of cousins. Other results concerning the distribution of cousins include Euler's proof that the sum of the reciprocals of cousins diverges, and the Goldbach conjecture, which says that any number large enough that is the sum of two primes. Yet another conjecture related to the distribution of prime numbers is the Riemann hypothesis, formulated by Bernhard Riemann in 1859. The prime number theorem was finally proven by Jacques Hadamard and Charles de la-Vallée Poussin in 1896.
An airline provides air transport services for passengers or cargo, usually with a recognised certificate, or operating license. Airlines lease or her own aircraft, with which these services can be delivered in partnerships or alliances with other airlines for mutual benefit. Airlines are people with a single e-mail with the aircraft or cargo through full-service international airlines many hundreds of aircraft. Airline services can be seen as intercontinental, intracontinental, or home and can be operated as scheduled or charter. Tony Jannus, the United States' first commercial flight scheduled on 1 January 1914 for the St. Petersburg-haul, through mergers and the time involved in the Delta Air Lines, Braniff Airways, American Airlines, United Airlines (originally a division of Boeing), Trans World Airlines, Northwest Airlines and Eastern Air Lines , to name just a few. At the same time, Juan Trippe began a crusade to create an air network that would America in the world, and he achieved this goal through its airline, Pan American World Airways, with a fleet of flying boats that, in conjunction with Los Angeles and Shanghai Boston to London. Pan Am was the only US airline to the international business before the 1940s. KLM, the oldest carrier, under its original name, was founded in 1919. The first flight (on behalf of KLM by the Aircraft Transport and Travel) transported passengers on two English Schiphol, Amsterdam from London in 1920. Like the other major European airlines of the time (see France and the United Kingdom below), KLM early growth depends to a large extent on the needs for service links with far-flung colonial possessions (Dutch East India). It is only after the loss of Empire, that the Dutch KLM found itself based on a small country with only a few potential passengers, depending heavily on the transfer, and was one of the first to the hub system to facilitate easy connections. France began an air-mail service in Morocco in 1919, was purchased in 1927, renamed Aéropostale, and with capital injected into one of the leading international carriers. In 1933, Aéropostale went bankrupt, was nationalized and merged with several other airlines in what was Air France. In Finland, the charter establishing Aero O / Y (now Finnair, one of the oldest still in operation airlines in the world) was in the city of Helsinki on 12 September 1923. Junkers 13 D F-335 was the first aircraft of the company, on the supply of Aero he took on 14 March 1924. The first flight was between Helsinki and Tallinn, the capital of Estonia, and it took place on 20 March 1924, a week later. Lufthansa in Germany began in 1926. Lufthansa, in contrast to most other airlines at the time, was a major investor in airlines outside Europe, the capital of Varig and Avianca. German aircraft built by Junkers, Fokker and Dornier were the most advanced in the world at that time. The highlight of the German air traffic came in the mid-1930s, as Nazi propaganda minister, the start of commercial zeppelin service: the great airships were a symbol of industrial might, but the fact that they are flammable hydrogen gas increases Security concerns, which culminated with the Hindenburg disaster of 1937. The reason why they are with hydrogen instead of the non-flammable helium gas United States was a military embargo on helium. The British company Aircraft Transport and Travel began in London for Paris on 25 th August 1919, it was the world's first regular international flight. The United Kingdom's flag carrier during this period was Imperial Airways, the BOAC (British Overseas Airlines Co.) in 1939. Imperial Airways uses huge Handley-Page biplanes for the routes between London, the Middle East and India: Images of Imperial plane in the middle of the Rub'al Dalip Singh, is maintained by Bedouins, are among the best-known images from the heyday of the British Empire. The first country in Asia to embrace the aviation sector in the Philippines. Philippine Airlines was on 26 In February 1941, making it Asia's oldest still in operation carrier under its current name. The airline was founded by a group of businessmen headed by Andres Soriano, celebrated as one of the Philippines' leading industrialists at the time. The airline first flight took place on 15 March 1941 with a single Beech Model 18 NPC-54 aircraft, its daily service between Manila (from Nielson Field), and Baguio, later expanding with larger aircraft such as the DC - 3 and Vickers Viscount. In particular, Philippine Airlines leased its first Japan Airlines plane, a DC-3 named "Kinsei". On 31 July 1946, a chartered Philippine Airlines DC-4 transports 40 American soldiers Oakland, California Nielson from the airport in Makati City with stops in Guam, Wake Iceland, Johnston Atoll in Honolulu, Hawaii, PAL, the first Asian airline to cross the Pacific Ocean. A regular service between San Francisco and Manila began in December. It was in that year that the airline was, as a carrier of the Philippines flag. Another airline to begin operations early was Air India, which had its beginnings as Tata Airlines in 1932, a division of Tata Sons Ltd (now Tata Group) of India's leading industrialist JRD Tata. On 15 October 1932, JRD Tata himself flew a single-engined De Havilland Puss Moth, air-mail (mail from Imperial Airways) from Karachi to Bombay via Ahmedabad. The aircraft continued Madras Bellary on the pilots of the Royal Air Force pilots Nevill Vincent. After the end of World War II, regular commercial service was restored in India and Tata Airlines, a joint stock company on 29 July 1946 under the name Air India. After the independence of India, 49% of the airline was purchased by the Government of India. In return, the airline status has been granted to international services from India, as the designated flag carrier under the name Air India International. Neighbouring countries are also quickly embraced aviation, in particular Cathay Pacific, founded in 1946, Singapore Airlines and Malaysian Airlines in 1947 (as Malayan Airways), Garuda Indonesia was founded in 1949 and Japan Airlines in the year 1951. With the outbreak of the Second World War, the airline presence in Asia came to a relative standstill, with many new flag carrier donate their aircraft for military assistance and other uses. World War II, like World War I, brought new life for the airline industry. Many airlines in the Allied countries were flush from leasing contracts for the military, and saw a future explosive demand for civil air transport for passengers and freight. They were eager to invest in the new flagships of air travel as the stratosphere Cruiser Boeing, Lockheed Constellation, and Douglas DC-6. Most of these new aircraft were based on the American bombers like the B-29, had the forefront of research into new technologies such as pressurization. Most of increased efficiency offered by both added speed and greater payload. The next big push for the airlines were in the 1970s, when the Boeing 747, McDonnell Douglas DC-10, and Lockheed L-1011 inaugurated widebody aircraft ( "Jumbo Jet"), which is still the standard in international travel . The Tupolev Tu-144 and its Western counterpart, Concorde, the supersonic travel a reality. In 1972, Airbus began production in Europe, the most commercially successful line of aircraft to date. The added value for the efficiency of these aircraft were often not in speed, but in the passenger capacity, payload and range. As the economy back to normalcy, major airlines dominate their routes through aggressive pricing and additional capacity offers, which are often overloaded new startups. Only America West Airlines (since the merger with US Airways) remains an important survivor from the era of new entrants, as dozens, even hundreds, have at. In many ways, the biggest winner in the deregulated environment was the passenger. Indeed, the US witnessed an explosive-growing demand for air travel, how many millions who have never or rarely been flown before regular fliers, including the accession of the frequent flyer programs and loyalty, free flights and other benefits from their flying . New services and higher frequencies means that business fliers could fly to another city to do business, and return the same day, for the almost anywhere in the country. Air travel benefits brought intercity bus lines under pressure, and most of them collapsed. So in the last 50 years, the airline industry from varied quite profitable, devastating depressed. As the first major market to deregulate the industry in 1978, US airlines have more turbulence than almost any other country or region. Today, almost every single legacy carrier with the exception of American Airlines, under the provisions of Chapter 11 bankruptcy, or gone out of business. Many countries have national airlines that the government owns and operates. Full private airlines in a lot of government regulation for the economic, political and security concerns. For example, the government often uses to stop airline labor actions to protect the free movement of people, communications and goods traffic between the various regions, without compromising security. The United States, Australia and to a lesser extent, Brazil, Mexico, Great Britain and Japan have "deregulated" their airlines. In the past, these governments dictated airfares, route networks and other operational requirements for the various airlines. Since deregulation, airlines have largely been free to negotiate their own operating costs agreements with various airports, entering and leaving tracks easily, and to collect and airfares flights according to market demand. The entry barriers for new airlines are lower in a deregulated market, and so has seen the US-hundreds of airlines start (sometimes only for a short period of time operating system). This is far more than before the deregulation of competition in most markets, and the average prices tend to fall 20% or more. The added competition, along with the pricing freedom, it means that new entrants often share of the market with reduced rates, to a certain degree, full-service airlines have to match. This is a major obstacle to profitability for the established aviation companies, which usually have a higher cost. Groups such as the International Civil Aviation Organization establish worldwide standards for safety and other important issues. Most international air transport is governed by bilateral agreements between countries, certain media on the operation of certain routes. The model of such an agreement was the Bermuda agreement between the United States and Britain after the Second World War, the specific airports, in transatlantic flights, and every government has the authority to nominate air carriers to operate routes. Bilateral agreements are based on the "freedoms of the air", a set of generalized traffic rights of the freedom to fly over a country of freedom to provide domestic flights within a country (very rarely granted right known as cabotage). Most agreements allow airlines to fly from their home country to certain airports in other countries: in some cases, the freedom to provide continuous service in a third country, or to another destination in the other country, while the passengers from overseas. In the 1990s, "open-skies" agreement was frequent. These agreements take many of these regulatory powers of state governments and international routes open to competition. Open Skies agreements have met some criticism, particularly within the European Union, whose airlines would be at a comparative disadvantage with the United States "because of cabotage restrictions. One argument is that positive externalities, such as higher growth through global mobility , which outweighed the microeconomic losses and continued to justify government intervention. a historically high level of state intervention in the airline industry can be seen as part of a broader political consensus on the strategic forms of transport, such as highways and railways, both from the public funding in most parts of the world. profitability improvement is likely in the future as privatization continues to be competitive, and more low-cost carriers proliferate. due to the complications in scheduling flights and the maintenance of profitability, the airlines have many loopholes that can be used by the experienced traveler. airfare Many of these secrets more and more known to the general public, the airlines forced to constantly adjustments. most airlines use differentiated pricing, a form of price discrimination to services sell air simultaneously different prices for different segments. influence factors on the price, the remaining days until the departure, the booked load factor, the forecast of total demand for price, competitive prices in force, and variations from day of the week and the departure of the time of day. Carriers often achieve this by dividing each cabin of the aircraft (First, Business and Economy) in a series of travel classes for pricing. complicated One factor is that the origin-destination (O & D control ") . Someone buying a ticket from Melbourne to Sydney (as an example) for 200 Dollars (AUD) competes with someone who wants to fly to Los Angeles Melbourne through Sydney on the same flight, and who is willing to pay 1400 dollars (AUD). If the airline prefer the $ 1400 200-1300? Airlines have to hundreds of thousands of daily decisions similar pricing policy. The introduction of modern computerized reservations systems in the late 1970s, especially Sabre, airlines allowed to easily carry out cost-benefit analyses of different pricing structures, which almost perfect price discrimination in certain cases (that is, filling every seat in an aircraft at the highest price may be required, without the consumers elsewhere). Price discrimination is an anti-business practice and is defined as price discrimination definition: different prices for identical products. Technically, is the sum of the specific activities of the other airline, without violating laws. The archaic airlines with hub systems and unprofitable pricing structures, have legally defines this term as an attack on the company, even if this law is not outside the law. The low-cost carriers (LCC) are new to the scene and does not have the resources to contact or outlaw this definition of a purely legal business practice (in which they are to participate) as monopolistic practices which have the above-mentioned archaic tariff structure . The national airlines still to be defined as the discrimination is a harmful and detrimental intenionally wanted to act on their business with a competitor. Laws for the protection of the business can be applied, or those who have the greatest impact in May insinuate, without proof that they are unfairly treated, and thus their legal status as the defendant to limit manuevaribility LCC's in the market. One example is that it taxes demand from the US government for certain airports, for the nation or exemption receive grant for either a) seniority / grandfathering treatment, or b) the legal position as a financially on the edge (ie bankruptcy) . The intensive nature of the airline ticket pricing has led to the term "rate war" to describe efforts by airlines to undercut other airlines at competitive routes. Through computers, new airfares can be published quickly and efficiently to the airlines distribution channels. To this end, the use of airlines Airline Tariff Publishing Company (ATPCO), the latest tariffs distribute more than 500 airlines in the computer reservation system in the world. Full-service airlines have a high level of fixed and operating costs, to the creation and maintenance of the air: labor, fuel, aircraft, engines, spare parts and components, IT services and networks, airports, airport handling services, sales, catering - -, training, aviation insurance and other costs. Therefore, all but a small percentage of revenue from ticket sales is paid out to a variety of internal or external providers cost centers. The industry is structured so that the airlines often than Zöllner. Airline untaxed fuel is however due to a series of existing treaties between the countries. Ticket prices include a number of fees, taxes and surcharges they have little or no control over, and these are passed through to different providers. Airlines are also responsible for the enforcement of state regulation. If the airlines carry passengers without proper documentation on an international flight, they are responsible for the repatriation of them back to their country of origin. In contrast, Southwest Airlines was the most profitable companies in the airline since 1970. Indeed, some sources have calculated Southwest, the best performing stock over the period, outperforming Microsoft and many other high-performance companies. The chief reasons are that their product consistency and cost control. The widespread entrance of a new generation of low-cost airlines from the turn of the century, the requirement that full-service carrier costs. Many of these low-cost companies emulate Southwest Airlines in a variety of ways, and how Southwest, they are able to eke out a consistent profit in all phases of the economic cycle. Consequently, a shakeout of airlines, in the United States and elsewhere. United Airlines, US Airways (twice), Delta Air Lines and Northwest Airlines have declared bankruptcy, Chapter 11, and the American has hardly avoided. Alitalia, Scandinavian Airlines System, Sabena, Swissair, Japan Air System, Viasa, Air Canada, Ansett Australia, and others have flirted with or bankruptcy since 1995, as a low-cost provider in their home markets as well. Some argue that it would be far better for the industry as a whole, when a wave of closures were actually to reduce the number of "undead" competing airlines with healthy airlines simultaneously artificially protected from creditors on insolvency law. On the other side, some have pointed out that the reduction in capacity would be short-lived, since there would be large amounts of relatively new aircraft, would like to get rid of bankruptcies and would return to the market, either as increased for the fleets of survivors or the basis for the new airplanes cheap startups. Airline funding is fairly complicated, because the airlines are highly leveraged operations. Not only must they buy (or lease) and new airliner engines regularly that they have great long-term fleet decisions with the aim of meeting the needs of their markets while a fleet of production, which is relatively inexpensive to operate and maintain. Southwest Airlines compare and their dependence on a single type of aircraft (the Boeing 737 and derivatives), with the now lapsed Eastern Air Lines operated, the 17 different types of aircraft, each with different pilot, engine, maintenance and support needs . A second problem is that financial security of oil and fuel consumption purchases, which usually only seconds to complete its work in the relative costs for the companies. But with the current high gasoline prices, the biggest cost for an airline. While hedging instruments can be expensive, they can pay for itself many times over in times of rising fuel costs, as in the period 2000-2005. Given the apparent congestion at many international airports, the ownership of slots at certain airports (the right to land an airplane or off at a certain time of the day or night-time) has become a major tradable asset for many airlines. Obviously starting slots at popular times of the day can be critical in the production of more profitable business travelers to a specific airline flights and the creation of competitive advantage compared to a competing airline. If a certain city has two or more airports, market forces usually in the less profitable routes, or those on which the competition is weakest, to the less congested airport, where slots are likely to be more available and therefore cheaper. Other factors, such as land and maritime transport and onward transport links, will also affect the relative attractiveness of different airports and some long-distance must operate with the longest runway. Code-sharing is the most common type of airline partnership, and it includes an airline sells tickets for the flights of another airline, according to its own airline code. An early example was Japan Airlines' code-sharing partnership with Aeroflot in the 1960s on flights from Tokyo to Moscow: Aeroflot flights operated by Aeroflot aircraft, but JAL sold tickets for the flights as if they were JAL flights. This practice allows airlines to expand their operations, at least on paper, in parts of the world where they can not afford to bases or aircraft purchase. Another example was the Austro-Sabena partnership at the Vienna-Brussels-New York JFK route in the late 60's, with a Boeing 707 with Austrian Sabena colors. since airline reservation inquiries are often used by city-pair (such as "Show me flights from Dusseldorf to Chicago"), an airline, the code is in a position with another airline shares for a variety of routes should be in a position to actually offer as a Dusseldorf-Chicago flight. passenger is advisable, however, that the airline operates 1 say that the flight from Chicago to Amsterdam, 2 and the continuing airline operates flights (on another plane, sometimes from another terminal), to Düsseldorf. ensure that the primary motivation for the code-share is the expansion of its own service offerings in the city-pair conditions, increase sales. often combine the Enterprise IT operating, fuel purchase, purchase or aircraft as a block to higher bargaining power. However, the alliances were in the most successful shopping invisible supplies and services, such as fuel. Airlines usually prefer to buy visible to their passengers to distinguish itself from local competitors. If an airline, the main domestic rival Boeing airplanes flying, then the airline prefer Airbus aircraft to be used, regardless of what the rest of the alliance chooses. Everybody operator of a scheduled or charter flight airline uses a call sign when communicating with airports and air traffic control centers . Most of these call signs are from the airline trade names, but for reasons of history, marketing, or the need to reduce ambiguity in English is spoken (so that the pilots do not mistake the navigation decisions on the basis of instructions, to another plane) Some airlines and air forces to use call signs less obvious in connection with their trade names. For example, British Airways Speedbird uses a call-sign, named after the logo of its predecessor BOAC, while America West uses Cactus Corporate reflect that, in an apartment in the State of Arizona and are different from many other airlines with America and the West in their call signs. industry is cyclical. four or five years of poor performance before five or six years, the performance improved. But profitability in the good years is usually low in the order of 2-3% net profit after interest and taxes. times the profit, airlines lease new generations of aircraft and upgrade services in response to increased demand. since 1980 has The industry has not earned back the cost of capital in the best of times. Conversely, in bad times losses can dramatically deteriorated.
