American Airlines, Inc. (AA) is a major American airline headquartered in Fort Worth, Texas. Operating an extensive international and domestic network, American Airlines is the world's largest airline by fleet size and revenue, and the second largest by number of destinations served, after United Airlines. It operates from its main hub at Dallas/Fort Worth, and its hubs at Charlotte, Los Angeles, New York-JFK, New York-LaGuardia, Miami, Chicago-O'Hare, Philadelphia, Phoenix, and Washington, D.C., while its primary maintenance base is at Tulsa International Airport. Its primary competitors are United Airlines, Delta Air Lines, and Southwest Airlines.