Commercial flight Summary

  • Last updated on November 10, 2022

The transportation of passengers and freight by commercial airline companies.

The emergence of relatively reliable and safe airplanes during World War I induced people to attempt the organization of an airline to operate those craft on a scheduled basis over a consistent route. The Deutsche Luftreederei began service from Berlin to Leipzig and Weimar on February 5, 1919, followed only three days later by the French Farman Company on the cross-channel crossing from Paris to London using a converted Goliath bomber of World War I provenance. In August, 1919, the first daily service was established on this route from Le Bourget Airfield in Paris to Hounslow in the United Kingdom. The oldest surviving airline, KLM, was organized in the Netherlands in 1919 and, jointly with a British company, began flying the route between Amsterdam and London the following year. Outside of Europe, the Queensland and Northern Territories Aerial Services (Qantas) was founded in 1920. This eventually became the Australian national airline.

Most of the airlines founded in the 1920’s and 1930’s were created at least in part to encourage the purchase of aircraft of domestic manufacture. However, the privately owned Swissair was the first European airline to purchase American aircraft. The intertwining of domestic aircraft manufacture and national airline operation was widely advocated as critical to national defense.

In the United States, airline pioneers were private operators, as were the aircraft builders, and there was no national policy concerning either operation. Throughout the 1920’s there were no adequately financed airlines, and most lasted for only short periods before failing or merging. Given the large expanse of the United States, an airline with routes of national or even regional coverage was the exception. It was only in the late 1920’s that any thought was given to the question of encouraging a domestic aircraft industry or the promotion of domestic airline companies.

International Transportation

In Europe, in particular, the colonial airline emerged as a factor in the overall evolution of commercial aviation. Britain, France, and the Netherlands all developed colonial airlines, with Belgium, Italy, and the United States joining the operation less extensively. Routes for national airlines were limited to destinations within a country or its possessions, except by agreement. The extensive colonial empires still in existence in the 1920’s and 1930’s became natural sites for extended airlines. Britain, for example, created Imperial Airways by first using bilateral agreements with other European countries to reach the Mediterranean, and once there, to project a continuation based on British colonies and protectorates in Malta, Cyprus, Palestine, Trans-Jordan, Iraq and the Persian Gulf protectorates, India, Burma, the Malay Protectorate, Australia, and New Zealand. China, Central Africa, and South Africa could be reached by other routes. Only the North Atlantic and the northern Pacific resisted a “British” national airline. France shaped a colonial airline from Provence across the Mediterranean to Algeria, the French Sahara, French Equatorial Africa, and Madagascar. Working out the landing rights between Belgium and France provided a route to the Belgian Congo. The Netherlands, through trades with Britain, shaped a colonial route for KLM to the Dutch East Indies (present-day Indonesia).

In the 1930’s, these colonial routes were the main long-distance air routes available not only because a far-flung empire simplified the problem of securing landing rights but also because the operating stage, the maximum distance that might be flown without stopping to refuel, was then only about 500 miles. The Pacific and Atlantic oceans were the major water jumps that remained unconquered by civil aircraft in 1930. The American air routes showed the way to the solution. Pan American Airways was first organized to fly from Miami to Key West in Florida and to Havana, Cuba, and by the 1930’s from Brownsville, Texas, to Mexico City and Panama. Pan American founder Juan Terry Trippe advocated the concept of the “chosen instrument” or the idea that international connections for the United States should be provided by a single American company flying only outside of the country. The American “empire” in this sense was Latin America, where American investment was extensive but political control was only indirect. Germany, which after World War I lost its colonies, similarly turned to South America, particularly Colombia, to shape an extensive system of air routes. In the American case, Pan American’s ultimately extensive route structure in the Caribbean, on the east coast of South America, and in Central America provided experience in operating a long-distance international airline.

By the early 1930’s, three airlines in particular were seeking to develop world-scale route patterns: Pan American, Imperial Airways, and KLM. Such a development called for a set of aircraft that were entirely new in concept from those that had been derived from the planes of World War I. Specifically, what was needed were seaplanes, which offered some advantages. They could fly stages of considerably greater length than could be flown with standard land planes because the sea-based plane enjoyed an almost infinite takeoff runway, a long stretch of water in a sheltered embayment. Several miles might be used at a time when a 1,000-foot runway was the norm. Long runways, either on land or on water, meant that planes could be quite large, use multiple engines, have large enough fuel tanks to fly an extended stage, and require less strength in the undercarriage.

The tradition of high-powered planes introduced between 1907 and 1909 by American aircraft builder Glen H. Curtiss continued. In addition to the Curtiss Company, Martin and Sikorsky each produced large, four-engine seaplanes with the potential for stages of more than 500 miles. Because of its size, the United States showed a concern for lengthening the stage even of land-based planes. When Pan American adopted the seaplane in the early 1930’s, the Sikorsky S-42 flying boat had four engines that permitted it to fly to Buenos Aires, Argentina, by making a series of water crossings between Puerto Rico and the Rio de la Plata.

Airmail Service

After World War I, another factor contributed to airline development, namely the desire for an air service to speed up delivery of mail. Unlike Europe, where the nationalized airlines carried the mail, in the United States the Army Air Corps was assigned the job, with generally poor results. The problems of flying in a country the size of the United States were considerable. Particularly in the East, with the broad band of the Appalachian Mountains lying athwart the main routes, bad flying conditions were endemic and crashes were frequent. The introduction of aircraft beacons helped, but the low altitude at which most contemporary planes operated continued to plague service. Commercial flying began in earnest in 1925 when, under the Air Mail Act of 1925, also known as Kelly Act, the United States Post Office Department established contracts for carrying mail over assigned routes. Payments were made in return for the weight of mail carried. This practice often generated earnings that made the difference between marginal operation and flying at outright losses. Later, the method of airmail payments was revised. Instead of paying for the weight of mail carried, the Post Office paid instead for the space reserved for airmail, were it to be offered to the airline company to transport. The result was an incentive to the companies to increase the size of the planes that they normally flew.

Growth of the Aviation Industry

Competition for the airmail routes led to the formation of several large American aviation companies. William Boeing, who during World War I was a lumber producer in Seattle, Washington, had built planes from Sitka spruce, a wood with fibers of great tensile strength. Boeing bid on what came to be called the “Columbia Route” (New York City to California’s San Francisco Bay Area), winning the western segment from Chicago to Oakland. Henry Ford, who for several years had been building a trimotor plane, secured the route linking Cleveland and Chicago. To serve the western section, Boeing experimented with new and larger planes built by the Boeing Aircraft Company, which in the following sixty years became the world’s largest and most comprehensive civilian aircraft manufacturer. United Aircraft & Transport joined with National Air Transport (which later became United Air Lines) and others to create a second aviation company that secured the contract for the eastern segment of the Columbia Route, linking Chicago and New York City, and for the north-south route on the west coast from Vancouver, Canada, to Los Angeles. A further recipient of an airmail contract was the Aviation Corporation (North American and Curtiss aircraft builders), which became American Airlines. The General Motors Corporation held major ownership in Transcontinental Air Transport (TAT) as well as Eastern Transport on the north-south airmail route on the East Coast. With Pan American, which was assigned several foreign routes, these aviation companies constituted the “Big Five” airlines, which survived as the dominant U.S. carriers until the 1990’s.

Improvements in Aircraft Operation

In the late 1920’s, airlines were stymied by two problems: night flying and high-altitude flying. Both were still too dangerous for passenger transportation. In the United States, crossing the Appalachians was possible, as the operating ceiling of the planes exceeded the necessary 3,000 to 4,000 feet. In the Rocky Mountains and the western Coast Ranges, however, there were 8,000- to 10,000-foot passes. Continuous flight over a major part of the United States could not be accomplished during daylight hours.

In 1929, Transcontinental Air Transport and the Pennsylvania Railroad joined forces to solve, at least in part, these altitude and darkness problems. They organized a rail-plane route between New York City and Los Angeles. The “Airway Limited” departed New York’s Pennsylvania Station at 6:05 p.m., using a Pullman sleeper to reach Port Columbus, Ohio, a new landing field outside of the Ohio capital. There, passengers boarded a Ford Trimotor plane at 8:15 a.m., which carried ten passengers to Waynoka, Oklahoma, by 6:24 p.m., in time to board a second Pullman sleeper on the Santa Fe Railway at 11:00 p.m. This was to arrive in Clovis, New Mexico, at 8:10 a.m., when the passengers boarded a second plane to fly to Los Angeles, and, for through passengers, on to San Francisco by 7:45 p.m. The route avoided most night flying and any mountains over 5,000 feet.

Such an arrangement demonstrated the need for planes better than the Ford Trimotor, the workhorse of American carriers in the late 1920’s. By 1928, Ford had improved speed on his plane, from 100 miles per hour on the 1926 model to 120 miles per hour on the 1928 model, through the introduction of stronger radial engines that were coming into use in the United States. By 1929, the United States was building 5,500 aircraft, up from only 60 five years earlier. The Vega of 1927 had increased cruising speed up to 150 miles per hour.

In 1930, Boeing’s Monomail demonstrated the virtues of all-metal planes with the installation of retractable landing gear. Most experts view the Boeing 247 of 1933 as the first modern commercial aircraft. It showed that twin-engine planes were safer than trimotors because they could be maneuvered more easily and might be flown on a single engine. So many of the planes were ordered that when Transcontinental and Western Airlines (TWA) sought to order some, Boeing declined. TWA turned to a smaller builder, the Douglas Company, and commissioned a similar plane as a trial. The prototype was the DC-1. In its developed form as the DC-2 and DC-3, it proved to be the most significant commercial plane ever constructed.

The DC Planes

The plane was first introduced as a prototype (the DC-1) in 1933 and put into production as the DC-2 (and in evolved form as the DC-3 in 1936). The first DC-2 was put in service on the Newark-Pittsburgh-Chicago run, after only 11 months development time. In an era when American engine builders were introducing new and more powerful engines at a regular and rapid rate, the Wright Engine Company had been able to substitute an improved and more economical engine by the time that quantity production began. American Airlines asked for a slight enlargement of the DC-2. When fitted out with seats, this enlargement held twenty-one passengers and was called a DC-3. As such, it was the first airliner to operate at a profit with a reasonable load factor. The DC-3 had a ceiling above 5,000 feet, could fly on only one engine, and with a stressed aluminum sheathing, was a strong plane with a retractable landing gear. In the ten years of its production life, the DC-3 became the unrivaled master airliner, carrying the majority of American traffic. It was found in the fleets of most of the world’s airlines, was used for military cargo (as the C-47 in the United States and as the Dakota in Britain), and was constructed in a run of more than 13,000 planes. Undoubtedly the greatest contribution of the DC-3 was that it demonstrated with great clarity the feasibility of safe, reliable, affordable, and profitable flying. Flying was a curiosity when the DC-3 was first built but had become standard transportation by the time of its last manufacture.

Between 1927 and 1939, the smaller aircraft engine rapidly advanced in its technology. Before World War I, the Russian aeronautical engineer Igor Sikorsky had constructed a twelve-engine flying boat. In the progression from DC-1 through DC-3, knowledge secured from earlier expressions of a basic design was used to enlarge that design so as to gain size, speed, and economy. Certain general qualities were standardized. The typical DC plane had a squarely rounded fuselage, a low wing, a particular way of carrying engine pods, and other features that had become standard. For example, if a larger passenger load was sought, the fuselage would be lengthened rather than widened. A longer plane required no other changes than enlarging the engines. Engines could be made more powerful by turbocharging them (supercharging them using centrifugal blowers driven by exhaust gas turbines), enlarging the cylinders, and making other mechanical elaborations. American aircraft builders became very adept at securing more power to go faster, farther, or cheaper.

The Four-Engine Plane

During the 1930’s, American airline operators increasingly sought ways of constructing and operating four-engine planes, recognizing that such aircraft could potentially fly above altitudes normally characterized by turbulence. Consequently, the Boeing Stratoliner was introduced in 1940. Equipped with a pressurized cabin and capable of flying at 14,000 feet at a speed of 200 miles per hour, the Stratoliner had just begun service during the second year of World War II. Development of this pioneering four-engine plane was taken over by the U.S. government for the duration of that conflict. The Stratoliner was the only commercial aircraft able to be flown directly from Newfoundland, Canada, to Northern Ireland during World War II. With its powerful supercharged engines, the Stratoliner could navigate not only above weather but also over mountains, rather than around them. Thus, routes could be chosen because they formed parts of great circles on the earth’s surface and were therefore the shortest possible distances between two points.

A second four-engine plane was designed just before World War II when the general configuration of the DC-3 was transformed into a four-engine size. Unlike the Stratoliner, this was not a pressurized plane, so it represented the last phase of one line of advance rather than the beginning of a postwar design. The enlarged DC-4 was flown throughout the war, becoming the main transatlantic aircraft in the form of the United States Army’s C-54 troop transport.

Postwar Developments

After World War II, air transportation was quickly restored to civilian life. The Stratoliner and the DC-4 began immediate service on the longer routes, even across the Atlantic and Pacific Oceans. Even more important was the introduction of a plane that for one decade became the principal competitor of the DC-4, the Lockheed Constellation. The rapid growth in the power produced by American aircraft engines encouraged TWA to turn to the Lockheed company in search of a plane that would add more than 100 miles per hour to the speed of the DC-3 (175 miles per hour) rather than the marginal 25-mile-per-hour increase of the DC-4. In addition, TWA engineers sought to lengthen the stage of planes so that a single-stop transcontinental flight was possible in either direction. When it entered service, the Constellation had an 80-mile-per-hour speed advantage over the DC-4. When the Super Constellation went into service in 1957, it weighed twice as much as its precursor, was considerably faster, and carried a much increased payload.

The very rapid growth of air traffic in the ten years after 1945 called for a number of different planes to deal with extended routes and enlarging markets. In large part, this expansion could transpire because there was a market for used aircraft. As airlines strove to fly faster and with lengthened stages, more people switched from trains or ships to planes. By 1953, the DC-7 was put in service, with a stage of up to 3,000 miles and a speed reaching 300 miles per hour. By 1957, the number of passengers crossing the Atlantic by air was greater than by sea. Once jet planes came into service at the end of the 1950’s, flying the Atlantic accelerated to the point that little more than a decade of steamship service remained before the end of the Atlantic Ferry.

The Jet Era

The realization that planes of varying size and purpose could carry jet engines had a profound effect on commercial flight. It was anticipated that the jet would revolutionize the speed of air travel. What was rather unexpected was that it could sharply reduce its cost when provided by a jetliner large enough to carry an economical load. The Boeing 707 was so economical when it was placed in service by Pan American on October 26, 1958, that it played the role for commercial jets that the DC-3’s had played for piston planes. When the fan jet was substituted for the simple jet engine, the family of Boeing jets earned a reputation for economical working just as the DC-6 had in the last generation of piston planes. Within a few years, Boeing had developed specialized jets for nearly the full range of commercial flying. The Boeing 727 became an intermediate-range jet carrying more than one hundred passengers, rivaling in size the largest piston planes. Later, the Boeing 737 became the workhorse of North American airlines. When it was discovered that the cost of operating jets was considerably less per passenger mile than the cost of operating even the best piston-engine planes, flying grew rapidly and became quite common over considerably longer distances. The Boeing Company began planning what came to be known as a jumbojet, the 747. When placed in service in 1970, the 747 was capable of carrying up to about five hundred passengers, but most models were fitted out for about four hundred, with substantial space allocated for baggage, mail, and freight.

  • Baker, David. Flight and Flying: A Chronology. New York: Facts on File, 1994. A very comprehensive reference text on aviation history.
  • Heppenheimer, T. A. Turbulent Skies: The History of Commercial Aviation. New York: John Wiley & Sons, 1998. A comprehensive history of commercial aviation from the biplane era to the end of the twentieth century.
  • Jane’s All the World’s Aircraft, 2001-2002. New York: Franklin Watts, 2001. An exhaustive almanac of current civil and military aviation.
  • Van der Linden, F. Robert. Airlines and Air Mail: The Post Office and the Birth of Commercial Aviation. Lexington: University Press of Kentucky, 2002. The curator of air transportation at the Smithsonian Institution’s National Air and Space Museum tells the story of the Post Office’s influence in the development of American commercial aviation.

Airline industry, U.S.

Airmail delivery


American Airlines


Cargo aircraft

DC plane family

Jet engines



Lockheed Martin


Pan Am World Airways


707 plane family


Transatlantic flight

Transcontinental flight

Turbojets and turbofans

United Air Lines

Categories: History