American Airlines, Inc. is headquartered in Fort Worth, Texas and its regional affiliates, American Eagle and AmericanConnection, operate more than 3,400 daily flights, serving 250 cities in more than 40 countries. American Airlines employs nearly 82,000 employees worldwide while American Eagle employs approximately 13,000 employees. 

Continental Airlines, Inc. is headquartered in Houston, Texas and regional flights are operated by Continental Connection and Continental Express, under code-share agreement with Continental Airlines. Continental Connection is operated by CommutAir, Colgan Air, Cape Air and Gulfstream International Airlines. Continental operates more than 2,800 daily flights and serves 135 domestic and 132 international destinations. It employs over 45,000 employees and has annual earnings of over $3.5 billion 

Delta Air Lines, Inc. is headquartered in Atlanta, Georgia and began in 1928 as a crop dusting service and air mail delivery. As the company grew, it merged with or purchased other airlines, including: Northeast Airlines, Western Airlines, a part of Pan Am, Northwest Airlines amoung others. It has major operations in nearly every region of the world and a mainline fleet of more than 770 aircraft. Delta, through its SkyTeam partners, operates approximately 13,000 flights each day. It is currently the largest airline in the United States. 

United Air Lines, Inc., (United Airlines) is headquartered in Chicago, Illinois and offers flight destinations across North America, Central America, South America, Asia, Europe, and Africa. The airline has U.S. alliances with United Express, Great Lakes Aviation, Gulfstream International Airlines, Island Air and Mokulele Airlines. United Airlines and United Express operate approximately 3,300 daily flights and serve more than 200 domestic and international destinations. United employs 47,000 employees in the U.S. and worldwide.

US Airways, Inc., is headquartered in Tempe, Arizona and operates major hubs in Charlotte, Philadelphia, and Phoenix. Starting out in 1939 delivering air-mail under the name All-American Airways, US Airways has steadily transformed over decades of mergers and business acquisitions into the fifth largest airline in the United States. US Airways operates more than 3,000 daily flights, and serves 155 domestic and 44 international destinations. The airline employs more than 32,000 employees and serves approximately 60 million passengers each year.