United Airlines was the creation of aviation pioneer William
Boeing, who started out in the airplane business in 1916. His Boeing
Airplane Company, as it was then called, achieved the first
international postal delivery in 1919, and he went on to establish
United Aircraft Corp. in 1928. It was this UAC that acquired mail
and passenger service operator Pacific Air Transport on January 1,
1928, then renamed Boeing Aircraft & Transport Co., merged with
Pratt & Whitney Aircraft in early 1929 to form United Aircraft and
Transport Corporation (UATC).
UATC acquired America's first scheduled passenger services
carrier Stout Air Services on April 29, 1929, the nation's first
scheduled service (mail only) operator Varney Air Lines in early
1930, and finally National Air Transport (a large Chicago-based
mail-only carrier) on May 7, 1930.[1]
On March 28, 1931, UATC formed the corporation United Air Lines,
Inc. to manage its airline subsidiaries.Thus, United Airlines makes the claim to be the oldest commercial
airline in the United States by dint of its Varney acquisition.