ATA Airlines, Inc. – formerly known as American Trans Air and commonly referred to as ATA – was an American low-cost scheduled service and charter airline based in Indianapolis, Indiana. ATA operated scheduled passenger flights throughout the U.S. mainland and Hawaii, Puerto Rico and Portugal as well as military and commercial charter flights around the world. In its early days the airline flew charters on a worldwide basis and had bases in Chicago, Detroit, New York, Indianapolis, Oakland and Milwaukee. Later when it entered scheduled service the airline maintained focus cities at Chicago Midway International Airport, Honolulu International Airport, and Oakland International Airport.

The airline's parent company – New ATA Holdings, Inc. (the successor to ATA Holdings Inc., which was also once known as Amtran) – later changed its name to Global Aero Logistics, Inc. and purchased World Air Holdings, Inc. for $315 million in an all-cash transaction with the financial backing of the investment firm, MatlinPatterson. World Air Holdings, Inc. owned and operated North American Airlines and World Airways as two separate US-certified air carriers. ATA was North America's largest charter airline, and until its shutdown transported more troops for the United States military than any other commercial airline.

On April 2, 2008, ATA filed for Chapter 11 bankruptcy protection. ATA then announced it was ceasing all services, effective 4:00 am EDT, Thursday April 3, 2008, citing the unexpected loss of a major contract for its military charter business, as a subcontractor of FedEx Express, along with recent increases in jet fuel prices. Red-eye flights in the air at the time of the announcement proceeded to their destinations. Flight 4586 from Honolulu to Phoenix was the last ATA flight, departing almost two hours late at 12:10 am (HST) arriving April 3, 2008 at 8:48 am (MST).

Southwest Airlines owns and retains all ownership of the operating certificate and all assets held by ATA Airlines including trademarks, logos, etc. These were purchased for $7.5 million by Southwest while ATA was operating under bankruptcy protection.