This was the first major piece of legislation created by Congress in 1925 that would effect the aviation industry. In essence, this Act authorized the awarding of government mail contracts to private carries, established the rates for transporting mail and it set the airmail rates. Contracts were awarded through the United States Postal Service, and contracts were awarded through a bidding process. This legislation allowed the postal service to pay $3.00 per pound for mail transported by air carriers.

This Act inspired owners of aircraft and investors to start up air carrier services, providing airmail service. All American Aviation was one of several carriers that grew out of the Kelly Act. All American Aviation had procured airmail contracts from the United States Postal Service. The contracts were to deliver mail to and from Allegheny Mountain region of Pennsylvania, West Virginia and eastern Ohio.

Many Air carriers did not provide air passenger carriage as the carriage of mail was much more profitable and aircraft were limited in gross weight, roughly around 3,500 pounds. However, Airmail Act of 1930, encouraged airline carriers to purchase larger aircraft, increasing the likelihood of being awarded airmail contracts. It also stimulated the carriers to fill space on the aircraft with passengers.

In the Mid 1940's, All American Aviation changed its name to All American Airways, purchased larger aircraft such as the DC-3 and began carrying passengers. Throughout the 1940's, and early 1950's, All American Aviation began taking on new passenger and cargo routes. By the early 1950's, All American Aviation had over twelve DC-3 aircrafts.

In 1953, the air carrier again changed its name to Allegheny Airlines after the Allegheny mountains and river. This in recognition to which the carrier was based and the heart of the air carrier route system. Throughout the mid 1950's, and early 1960's, Allegheny operated Convair 440's, 540's and Martin Executives. By 1963, the carrier had a feet of 38 aircrafts which included 23 Convair 440's and 15 Martin Executives. Also during this year the carrier moved its maintenance, engineering, flight operations and flight control personnel from Washington to Greater Pittsburgh International Airport.

By the mid 1960's, and early 1970's, the airline carrier began providing commuter air service between Hagerstown, Maryland and Baltimore Washington International Airport, expanded its air routes to cover the mid west, New York and New England. The air carrier was able to expand into these markets as a result of a merger with Central Airlines based in Indianapolis, Indian and Mohawk Airlines based in Utica, New York.

With the passing of the Airline Deregulation Act of 1978 airline carriers were provided with new freedoms to expand their route systems and the flexibility to develop innovative pricing structures. This flexibility allowed the carrier to further grow into the markets of Arizona, Texas, Colorado and Florida. In 1979, Allegheny changed its name to US Air to reflect its growth within the United States.

By the late 1980's, the airline industry began to experience the consolidation of air carriers to become larger airlines due to high competition for air routes and passengers. US Air, in its desire to remain competitive, acquired Pacific Southwest Airlines and Piedmont Airlines. The merger of Pacific Southwest Airlines allowed US Air to expanded into the mid Atlantic markets. By 1983, US Air had revenues of over $80,000,000.