Prior to its official establishment, United Airlines was born from a small air mail operation run by Walter T. Varney on his Swallow biplane. Varney's company was purchased by William Boeing in 1927 and remained part of Boeing until 1934. United Airlines' official company history begins with its official establishment in 1934 as part of the separation of the United Aircraft and Transport Corporation due to the Air Mail Act.
United Airlines was one of three companies that came into existence due to the Air Mail Act, along with United Aircraft and the Boeing Airplane Company. Landmarks in United Airline's history include being the first airline to use modern flight simulators for pilot training in 1954 and its merger with Capital Airlines in 1961, which created the largest airline company in the United States.
In 1982, United Airlines became the first company to operate flights using the Boeing 767. The airline's purchase of Pan Am's Pacific Division in 1985 gave it access to an airport hub for Asian destinations in Narita International Airport. United Airlines attempted a merger with US Airways in 2000, but was unable to complete the deal after the merger was barred by the U.S. Department of Justice.
As of 2015, United Airlines flies to over 370 destinations and operate over 5,000 flights daily.