United Air Lines, Inc. is a major airline based in the United States and one of the world's largest airlines with 48,000 employees and 359 aircraft. It is a subsidiary of United Continental Holdings, Inc. formerly, UAL Corporation, with corporate headquarters in Chicago. United's largest hub is Chicago's O'Hare International Airport. United also has hubs in Washington Dulles International Airport, Denver International Airport, San Francisco International Airport, Los Angeles International Airport, and Narita International Airport near Tokyo. United is a founding member of the Star Alliance, the largest airline alliance in the world, and offers connections to over 1,000 destinations in over 170 countries worldwide.