Mail delivery also took a major turn during these years. In 1925, Congress passed the Kelly Air Mail act which authorized the Post Office Department to contract with air-transport operators. This made it possible to transport U.S. mail by air; after this, 14 domestic airmail companies were created in 1926.

VI. DURING WORLD WAR II

During World War II, aircraft became a decisive factor in warfare. The largest operator of all international airlines in operation at this time was Pan American Airways. Pan American served 46 countries and colonies linking all continents and nearly all oceans. Small aircraft production increased significantly. Before World War II only about 193,000 people were employed in the aviation industry, and during 1941 the number increased to 450,000; also, around 3,375,000 passengers were transported by 18 U.S. airlines at this time, around 1 million more than in 1940. Airmail and express cargo would also increase by around 30 percent. But by the end of World War II, a new frontier of flight would take shape, jet and rocket propelled aircraft.

VII. AFTER WORLD WAR II

After World War II and by 1947 all the basic technology needed for aviation had been developed: jet propulsion, aerodynamics, radar, etc. Civilian aircraft orders drastically increased from 6,844 in 1941 to 40,000 by the end of 1945. One of the minor military contractors was the Boeing Company who later became the largest aircraft manufacturer in the world. With all the new technologies developed by this time, airliners were larger, faster, and featured pressurized cabins. New aerodynamic designs, metals, and power plants would result in high-speed turbojet airplanes. These planes would later be able to fly supersonically and make transoceanic flights regularly.

One of the more famous record-breaking flights around this time was the Voyager, developed by Burt Rutan. The aircraft held 1,200 gallons (4500 liters) of fuel in its 17 fuel tanks. It weighed about 9,750 lb (4420 kg) at takeoff and only 1,858 lb (840kg) upon landing. The flight, maintaining an average speed of 115.8 mph (186.3 km/h), lasted 9 days, 3 minutes, 44 seconds and covered 25,012 miles (40254 km) and was completed in December 1986.