ATA Airlines, Inc. today announced that it has filed a voluntary petition under Chapter 11 of the U.S. Bankruptcy Code. The petition was filed on April 2 in the U.S. Bankruptcy Court for the Southern District of Indiana, in the Indianapolis division. Subsequent to the Chapter 11 filing, ATA discontinued all operations, effective as of 4 am ET on April 3. A primary factor leading to these actions was the unexpected cancellation of a key contract for ATA's military charter business, which made it impossible for ATA to obtain additional capital to sustain its operations or restructure the business.