United Airlines, Inc., commonly referred to as United, is a major United States airline headquartered in Chicago, Illinois. United operates a large domestic and international route network, with an extensive presence in the Asia-Pacific region. United is a founding member of the Star Alliance, the world's largest airline alliance with a total of 28 member airlines. Regional service is operated by independent carriers under the brand name United Express. United was established by the amalgamation of several airlines in the late 1920s, the oldest of these being Varney Air Lines, which was founded in 1926.United has seven hubs, with Chicago–O'Hare being its largest in terms of passengers carried and the number of departures. The company employs over 86,000 people while maintaining its headquarters in Chicago's Willis Tower. Through the airline's parent company, United Continental Holdings, it is publicly traded under NYSE: UAL with a market capitalization of over US$21 billion as of January 2018.