Aviation--the development, operation, and use of \Taircraft\t--refers primarily to the flight of heavier-than-air vehicles, but it also embraces the flight of lighter-than-air vehicles. Human-powered flight began in 1783 with the development of the hot-air \Tballoon\t by the \TMontgolfier\t brothers and the hydrogen balloon by J.A.C. Charles (1746-1823). The birth of practical heavier-than-air aviation came on Dec. 17, 1903, with the flights of Orville and Wilbur \TWright\t near Kitty Hawk, N.C. Aviation basically can be divided into three branches: military, commercial, and general. MILITARY AVIATION The balloon appeared as an airborne military observation post as early as 1794, in the battle of Maubeuge in France. Italy employed aircraft for reconnaissance during fighting in Libya as early as 1911. The major contributions made by reconnaissance aircraft during the opening stages of \TWorld War I\t gave the airplane major military significance (see \Taircraft, military\t). During the war specialized fighter-interceptor airplanes were also developed (see \TFokker D-VII\t; \TSopwith Camel\t). Equipped with machine guns, they marked the onset of air-to-air combat (called dogfighting) between opposing aircraft. The next move was to develop a strategic bomber. When its lighter-than-air Zeppelin proved unsatisfactory, Germany turned to large multiengine long-range airplanes, employing these in raids against England. In the \TUSSR\t, Igor \TSikorsky\t developed similar long-range bombers, based on his pioneering prewar work with large multiengine biplanes. Aircraft developers were soon designing specialized aircraft for light bombing, ground attack, and antisubmarine warfare. After 1918 a number of other specialized types were developed for military uses, including troop and cargo transport, medical evacuation, dropping of \Tairborne troops\t, and operation from naval \Laircraft carrier\ls. By 1939 the major air arms (see \Tair force\t) of the world's military forces had a variety of aircraft in service, developed for both strategic and tactical purposes. \TWorld War II\t demonstrated the power and importance of fighter, ground-attack, transport, and bomber aircraft and the vulnerability of ships to aircraft strikes. At war's end, the long-range bomber equipped with an atomic bomb emerged as the most powerful destructive weapon devised up to that time. Postwar military aviation developments have included supersonic fighter, bomber, and strike aircraft, extensive use of aerial refueling and large-scale military airlift operations, and the employment of sophisticated standoff weapons. The air-to-air guided missile has largely supplanted the airborne cannon as the primary armament of modern fighter aircraft. Increasing emphasis has been placed on the use of \Lhelicopter\ls for transporting assault forces and on attack helicopters using antiarmor and antipersonnel weapons. Advanced aircraft, such as the Lockheed SR-71A and the Soviet MiG-25 Foxbat (see \TMiG\t), are routinely capable of flying at three times the speed of sound (Mach 3). To counter modern fighter, bomber, and attack aircraft, ground forces are using \Tsurface-to-air missile\t (\TSAM\t) systems and radar-directed antiaircraft artillery, supported by sophisticated electronic warfare equipment for radar jamming and threat detection. COMMERCIAL AVIATION Commercial aviation began before World War I with the introduction of passenger-carrying Zeppelin \Lairship\ls in 1910; between 1910 and 1914 these airships carried more than 35,000 passengers between various German cities. After World War I, aviators around the world quickly initiated primitive air-transport ventures, using modified surplus military aircraft, such as the de Havilland D.H.4. On Aug. 25, 1919, a D.H.4A of Aircraft Transport and Travel Ltd. flew from London to Paris with one passenger and some cargo, initiating the world's first daily international civil airline service. By 1930, such international carriers as KLM (the Netherlands), Imperial Airways (Britain), and Pan American (United States) were already well established. The U.S. Post Office established a federally run \Tairmail\t service, eventually turning it over to private contractors. In 1926, Western Air Express began flying passengers. The notable Atlantic flight of Charles A. \TLindbergh\t in 1927 and the Daniel Guggenheim Fund for the Promotion of Aeronautics, established in 1926, were major forces acting to accelerate U.S. air transportation. The Guggenheim Model Air Line, with an extensive weather-reporting network and radio communications, was the prototype for both future airline management and airways development. In 1927 a total of 18,679 persons traveled by air; by 1931 the number had jumped to 385,000; in 1984 world airlines carried nearly 1 billion passengers. Advances in aircraft technology after World War I led from the open-cockpit biplanes of the 1920s to the high-wing, three-engine Fokker and FORD TRI-\Tmotor\t airplanes of the 1920s and early 1930s, and finally to the DC-3 (see DC-3), the first aircraft that could turn a profit simply by carrying passengers. The DC-3 featured such advances as all-metal stressed-skin construction, the radial engine, internally braced wings, retractable landing gear, and the controllable-pitch propeller. By 1938, DC-3s carried 95% of U.S. civil air commerce and had won wide foreign acceptance as well. Following World War I, Germany instituted transoceanic passenger Zeppelin flights across the Atlantic, but such operations were slow, disrupted by bad weather, expensive, and dangerous. The 1930s gave rise to the first transoceanic four-engine transports. In May 1919 the U.S. Navy's NC-4 flying boat had been the first airplane to fly (in stages) across the Atlantic. Twenty years later, on May 20, 1939, Pan American Airways launched the first U.S. commercial air operations to Europe, using the Boeing Model 314 Yankee Clipper flying boat. Following the loss of the Zeppelin \THindenburg\t in an explosion and fire in 1937, the flying boat quickly replaced the Zeppelin over the Atlantic, rendering the rigid airship obsolete. The flying boat itself, however, soon disappeared (see \Tseaplane\t). The world's first major four-engine transport was the Boeing 307 of 1938; it was the first high-altitude transport designed with a pressurized cabin. Soon after came the wartime Douglas DC-4 of 1942. The DC-4 eventually led to the pressurized DC-6 and DC-7 series. U.S. dominance of air transportation continued after World War II; in 1951, 80% of the world's airliners were U.S.-built, and of these, 56% came from Douglas. Technology continued to influence transport-aircraft design and operation. Britain developed (1948) the first turbo-propeller airliner, the Vickers-Armstrong Viscount, following this a year later with the first pure-jet gas-turbine-driven airliner, the de Havilland Comet. The United States lagged behind Britain in the development of jet airliners, preferring to stick with the proven radial engine; the Comet's introduction into scheduled service in 1952, however, acted as a catalyst for U.S. jet-airliner development. By 1950, Boeing had embarked on a jet-tanker-transport development program that eventually led to the soon-common sweptwing, podded-engine configuration of the Boeing 707. The jetliner quickly replaced the ocean liner as the dominant passenger carrier on the North Atlantic; more than 1 million passengers flew the Atlantic in 1958, for the first time surpassing the total carried by ocean liners. As the number of piston-engine transports declined, the number of jetliners in service quickly rose. Feeder airlines to service local regions expanded rapidly in the 1960s, and by 1970 feeder lines in the United States carried 27 million passengers annually. Civil-aviation operations rapidly expanded in the 1960s, encouraging the development of two new ventures in air-transport technology, the jumbo, or wide-body, superjet and the \Tsupersonic transport\t (\TSST\t). The first wide-body superjet, the Boeing 747, flew on Feb. 9, 1969. It entered service in 1970 and was quickly followed by other superjet designs. In 1971, as a result of rising environmental and economic concerns, Congress canceled the U.S. \TSST\t program. The Anglo-French \TSST\t, the \TConcorde\t, entered scheduled service in 1976, and the Soviet \TSST\t, the Tupolev Tu 144, in 1977. Serious economic problems encountered immediately in \TSST\t operations led to the suspension of production of the Concorde by the British and French governments in 1979. In 1984 production was suspended for the Boeing 727, the largest selling commercial jetliner in history. The 1,832 727s produced carried some 2.5 billion passengers a total of 21.4 billion miles. Air freight operations are a rapidly growing branch of commercial air transport. Shipping cargo by air is particularly advantageous for high-value goods, such as auto parts, chemical and pharmaceutical products, and livestock, and for such trade routes as the North Atlantic, on which alternate modes of transportation are slow. Cargo is shipped in passenger aircraft with converted interiors; \Tcontainerization\t is often used. By 1984, some two dozen all-cargo lines in the United States were competing for 8.2 ton miles of freight. GENERAL AVIATION General aviation is a term that refers to all civil aeronautics with the exception of commercial air-transport operations. It is a diverse field, covering sports flying (see \Taerial sports\t), business flying, crop-dusting, and numerous other operations. In 1982, fully 98% of active civil aircraft registered in the United States were classed as general-aviation aircraft. These ranged from small 240-km/h (150-mph) two-seat, single-engine trainers through 800-km/h (500-mph) plush business jet aircraft equipped with turbojet propulsion and extensive electronic installations. General aviation is often overlooked because, unlike military and commercial aviation, its aircraft requirements have fluctuated widely and have never been clearly defined. Beginning with pre-World War I exhibition flying and post-World War I BARNSTORMING, which popularized aviation, however, general aviation has been a vital part of air traffic. The first major U.S. general-aviation airplane was the Aeronca C-2, marketed in 1929; its European counterpart was the de Havilland Tiger Moth. The best-known general-aviation airplane of all time was the ubiquitous \TPiper Cub\t, which first appeared in 1937. Other aspects of general aviation include home-built aircraft and soaring craft. AIRCRAFT MANUFACTURE The first manufactured aircraft in aviation history was the Lilienthal Type 11 \Tglider\t, which the pioneer Otto \TLilienthal\t built and sold to enthusiasts in Europe and the United States in the late 19th century. Before World War I, many aircraft were literally handcrafted, in part because their structure and fittings were complex. The urgent demands of World War I, however, led to the development of rapid manufacturing techniques for the basically wood-and-wire aircraft of that period. Companies developed forming techniques permitting the construction of wooden monocoque (single-shell) fuselages. During the 1920s, following the work of Hugo Junkers (1859-1935) in wartime Germany, manufacturers developed techniques for metal construction. Claude Dornier (1884-1969), Adolf Rohrbach, and John \TNorthrop\t made notable contributions to the development of metal aircraft. Northrop's work on metal monocoque and multicellular wing construction foreshadowed techniques used on the design of most subsequent stressed-skin all-metal aircraft. During World War II, mass-production techniques and support from outside industries permitted production of U.S. military aircraft to exceed 300,000 airplanes. Postwar challenges to manufacturers included those of transonic and supersonic flight. Once thought to be a barrier to future flight development, the speed of sound (Mach 1) was surpassed by the experimental Bell X-1 rocket-powered research aircraft, piloted by Capt. Charles E. Yeager (1923- ), on Oct. 14, 1947. The first production supersonic aircraft was the North American F-100 Super Sabre jet fighter. During the early 1950s the \Taerospace industry\t took part in the development of long-range guided missiles, and related technologies immediately assumed key importance. These included computer systems, electronic controls, combustion chemistry technology, and advanced structural technology, such as the use of composite structures. The heavy investment in this sophisticated equipment lengthened research and development times for new aircraft and boosted costs. A 1945 fighter plane cost about $51,000. By the late 1980s, fighter aircraft development costs had soared into the multi-billion-dollar range. Transport aircraft costs rose proportionately. GOVERNMENT REGULATION The development of aviation has required a strong partnership between government and private industry. In Europe before World War I a number of scientifically trained engineers formed research organizations and laboratories, the most notable of these efforts being Britain's Advisory Committee for Aeronautics (1909) and the aerodynamicist Ludwig Prandtl's research center at Gottingen, Germany. In 1915 the United States created the National Advisory Committee for Aeronautics, the predecessor of the \TNational Aeronautics and Space Administration\t (\TNASA\t), established in 1958. Both agencies developed a number of new concepts (among them the variable-density \Twind tunnel\t; the transonic research airplane; the variable-sweep wing, winglets, and the oblique, or scissors, wing) that greatly benefited the development of advanced capability aircraft. In addition, governmental regulation has been crucial to the growth of commercial and general aviation, both abroad and in the United States. In 1925, the U.S. Congress passed the Kelly Act, approving federal subsidy of the airmail service and encouraging the growth of private-sector airmail carriers. The Air Commerce Act of 1926 marked the first federal attempt to impose safety regulations on civil aeronautics and required the registration and licensing of pilots and planes. Since that year several legislative acts have enlarged the scope of federal regulation both of air safety and of commercial routes and fares. The \TFederal Aviation Administration\t, under the Department of Transportation, regulates all aspects of airplane and airport safety and runs the vast air-traffic-control system. The \TCivil Aeronautics Board\t (CAB), an independent agency, was charged with regulating routes and fares. The passage of the Air Transport Deregulation Act (1978), however, freed U.S. domestic airlines from most governmental restraints on fares and scheduling, and the CAB's authority was slowly scaled back until, in 1984, its functions were taken over by the Department of Transportation. U. S. and foreign airlines fly a wide variety of aircraft, many of them designed and manufactured in the United States. European industries have produced their own successful designs, among them French Caravelle, Europe's most popular aircraft during the 20 years (1955-75) it was produced. Airbus Industrie a 5-nation European consortium, competes successfully with U. S. manufacturers with its A300 and A310 widebodies. Its mid-range 320 was a best-seller even before it made its first commercial flight in April 1988. The 320 "flies by wire"--it uses computerized electronic controls rather than the usual hydraulic or cable systems. A June 1988 crash at a French air show did little to reduce enthusiasm for the plane, which had been tested on nearly 800 flights before its commercial sales began. Airlines in the United States ordered over 100 delivery in 1989. An accident in April 1988, involving the tearing away of a large portion of the upper fuselage of a Boeing 737, has brought into focus a major aviation problem. The 737 had made 88,000 flights; cabin air pressure and the corrosive effects of seawater had weakened the fuselage panels. In earlier years, aging planes were no problem, because rapidly advancing technology retired aircraft--at least for regular airlines--before they could suffer the effects of aging. Many older aircraft have now been subjected to metal fatigue tests, and the FAA has proposed a rule that would limit the number of flights a plane can make during its lifetime. AIRPORTS Regulation of aviation has led to improvements in \Tairport\t and airway facilities. The first airports were usually grass strips or open fields; for most communities, asphalt and concrete runways came later, during the 1930s. In 1926 the U.S. federal government listed only 3,285 km (2,041 mi) of controlled civil airways--airways having beacon lights and some weather-forecasting aids. By 1940 this number had jumped to 51,660 km (32,100 mi). As airways developed, radio navigation aids were increasingly used. The first federal Air Route Traffic Control Center began operating in 1936, and in 1941 the first Instrument Landing Systems were placed in civil aeronautics service. The postwar Federal Airport Act (1946) accelerated airport expansion and construction. The year 1950 witnessed the first use of VOR (VHF Omnidirectional Range) transmission, which sends a flight-path signal to approaching planes. With the explosive expansion of jet travel, air-traffic control has become increasingly sophisticated. Radar stations now provide coverage of all airspace over the continental United States, and computers are used to automate much of the system. International air traffic uses Omega, a navigational system in which signals are broadcast from eight global transmission sites. On-plane computers calculate aircraft position by an analysis of the signals. The \TInternational Civil Aviation Organization\t (ICAO), an agency of the United Nations, facilitates compatibility of navigational equipment and procedures for air traffic on international routes. Regional groups help coordinate air traffic in Europe, the Middle East, and Africa. Richard Hallion THE AIRLINES Worldwide about 600 airlines are engaged in passenger and cargo operations. The United States operates the largest scheduled airline fleet, numbering more than 4,500 aircraft, and carries the largest number of passengers, over 400 million annually in the late 1980s. The U.S. industry, which had been relatively stable for many years, began to change dramatically after the deregulation of 1978. Price wars erupted on the popular long-haul routes while fares soared on shorter routes, and major airlines eliminated service to some smaller cities altogether. Experiencing increased competition, rapidly rising fuel prices, and an economic recession, many airlines attempted to strengthen their positions by expanding, merging, or juggling routes. A flock of small "commuter" lines arose to take over the short routes vacated by the major carriers. Some of the larger lines overexpanded and were then hard hit by high interest rates on newly purchased equipment. By the last half of the 1980s, a completely new structure had evolved. The most powerful lines included two giants from the days of regulation--American and United--and three others that had begun as regionals but had enlarged by swallowing other weaker carriers--Northwest, Delta, and Texas Air (Continental). These five shared over 75 percent of all commercial air traffic, achieving their near monopoly by controlling space at the nation's major airports, by fine-tuning fares daily, and by forcing wage reductions on their employees. The year 1989 alone saw several major changes in the industry: Eastern, a once-major airline now owned by Texas Air, declared bankruptcy and sold its northeast shuttle service to real estate tycoon Donald Trump; Northwest Airlines was bought by a group that includes KLM Royal Dutch Airlines; Braniff Airlines went bankrupt for the second time in seven years; and United was up for sale. American and foreign airlines fly a wide variety of aircraft, many of them designed and manufactured in the United States. The Boeing 727, a trijet introduced in 1963, was widely used during the 20 years it was produced. The twinjets Boeing 737 and Douglas DC-9 have each sold well over 1,000 planes to commercial airlines. The 4-engine Boeing 747 ushered in a new generation of wide-body types in 1969, including trijets like the DC-10 and the Lockheed L-1011. The wide-body Boeing 767 and the slimmer 757 entered service beginning in 1982. European industries have produced their own successful designs, among them the supersonic \TConcorde\t and the midsize French Caravelle, the continent's most popular aircraft during the 20 years (1955-75) it was manufactured. Airbus Industrie, a 5-nation European consortium, competes successfully with U. S. manufacturers with its A300 and A310 widebodies. Its mid-range 320 was a best-seller even before the first plane was produced in 1988. Roger E. Bilstein Bibliography: Ashford, N., et al., Airport Operations (1984); Biederman, Paul, The U.S. Airline Industry: End of an Era (1982); Bilstein, R.E., Flight in America, 1900-1983 (1984); Christie, J., High Adventure: The First 75 Years of Civil Aviation (1984); Emme, Eugene M., ed., Two Hundred Years of Flight in America (1977); Hallion, R.P., Legacy of Flight: The Guggenheim Contribution to American Aviation (1977); Kane, R. M., and Vose, A. D., Air Transportation, 9th ed. (1987); Layton, D., Aircraft Performance (1987); Morrison, S., and Winston, C., The Economic Effects of Airline Deregulation (1986); Serline, R.J., Eagle: The History of American Airlines (1985); Solberg, Carl, Conquest of the Skies: A History of Commercial Aviation in America (1979); Taneja, N. K., The International Airline Industry (1987).