United Airlines

United Air Lines, Inc., trading as United Airlines, is a major airline of the United States. It is a subsidiary of UAL Corporation with corporate offices in Chicago at 77 West Wacker Drive, and its operations base in nearby Elk Grove Township. United's largest hub is O'Hare International Airport, where it has 650 daily departures. United also has hubs in Denver International Airport, Washington Dulles International Airport, San Francisco International Airport, and Los Angeles International Airport. Its largest maintenance hub is the Maintenance Operations Center at San Francisco International Airport.

As part of the September 11, 2001 terrorist attacks, two United Airlines planes were hijacked by terrorists affiliated with al-Qaeda. One aircraft was a Boeing 767-222 (Flight 175) that crashed into the South Tower of the World Trade Center in New York City, and the other was a Boeing 757-222 (Flight 93) that crashed in rural Pennsylvania. The latter was suspected to have been directed towards the United States Capitol building according to the United States Department of Homeland Security. Only United and American Airlines were significantly affected on September 11, 2001.

United Airlines operates 3,300 flights a day to 210 destinations in 30 countries.