United Airlines came from somewhat humble beginnings in the early days of the US aviation industry.
William Boeing founded Boeing Airplane Company in 1916 as an aircraft manufacturer. With successful releases of Boeing Aircraft models, the company transitioned into operating as an air carrier for mail. The first successful mail delivery was in 1919. By 1928 a subsidiary, United Aircraft Corp, was established to operate as a full-service airline.
Under the United Aircraft Corp., the airline began to expand its business operations through a series of mergers and acquisitions across the US. United Aircraft Corp grew to include First Pacific Air Transport, Pratt & Whitney Aircraft, and Stout Air Services, who were already operating as a passenger airline.
A fast-growing airline, Varney Airlines, was also acquired by United Aircraft Corp, who had then become United Aircraft and Transportation Corporation (UATC). Founded by Walter Varney, Varney Airlines reflected modern airline operations after it expanded its business from mail to passengers using a Boeing 247 aircraft.