INDIANAPOLIS — ATA Airlines is suing FedEx Corp. over its decision to end a military charter business, a move the airline says forced it to seek bankruptcy protection and left it financially destroyed.

ATA accused FedEx of breaking a written agreement when it told the airline in January it would no longer receive military passenger service for the government fiscal year ending in 2009, according to a lawsuit filed yesterday in U.S. District Court in Indianapolis.

FedEx notified ATA of the cancellation in a letter that came "out of the blue," said Kenneth Broughton, a Houston-based attorney representing ATA.

He said ATA was counting on the military charters to be a "significant profit center."

The charter flights of military personnel and their families generated more than $400 million in annual revenue and were expected to remain a "cornerstone" of the airline's future business, the lawsuit states.

ATA filed for bankruptcy April 2 and abruptly ceased operations the next day.

The bankruptcy left some 10,000 customers of ATA stranded and scrambling in Hawai'i airports.

ATA operated about 50 flights a day between Hawai'i and Los Angeles, Oakland, Phoenix and Las Vegas. Those flights brought in about 770,000 passengers a year from the West Coast, making it the third-largest trans-Pacific carrier behind United Airlines and Hawaiian Airlines. ATA was once the nation's 10th-largest airline.

Fifty-eight workers in Hawai'i were laid off when the airline ceased operating.

ATA's shutdown came just two days after Aloha Airlines filed for bankruptcy and stopped flying passenger planes. The twin failures could cost the state millions of dollars in lost taxes, landing fees and airport rents, according to state officials.

FedEx spokeswoman Sandra Munoz said her company had no contractual obligation to ATA beyond the current fiscal year, which ends in September.

The military contracts commercial airlines for charter flights organized through two teams of companies.

ATA had flown military charter flights as a member of the FedEx team for more than 20 years. In late 2006, it spent more than $50 million to buy seven DC-10 planes from Northwest Airlines.

Broughton said the airline bought the planes and then spent additional money on hiring and training, because the military prefers wide-body aircraft. He said ATA did this after receiving a written commitment from FedEx that it would continue to receive military charter business through the fiscal year ending in 2009.

"There's absolutely no reason at all to buy a DC-10 except for these military flights," he said. "That's the only reason ATA bought them."

The airline had retrenched in 2006 after emerging from bankruptcy and was focused on increasing its military charter business. Broughton said the airline would have remained in business if FedEx had not canceled the contract.

The lawsuit asks for no specific damage amounts. Broughton said they were still tallying them but the total will be within the range of "tens of millions" of dollars.