When American Airlines' parent company, AMR Corp., acquired St. Louis-based Trans World Airlines in 2001, many locals saw it as nothing short of the rescue of the city's once-thriving airline hub.

But during a tumultuous decade in the airline industry, American has slid from the dominant carrier at Lambert-St. Louis International Airport to a distant second — after the repeated gashing of its flight schedule.

On Tuesday, when AMR filed for bankruptcy protection, Lambert officials learned there would be no immediate change to the daily flight offerings that now total 34. American officials made similar public assurances.

"I think we will be fine in St. Louis," said Lambert Director Rhonda Hamm-Niebruegge, who served as American's managing director in St. Louis. "I got a call from AMR (Tuesday) morning and they said … there would be no disruption to our passengers here."

American is the nation's third-largest airline and is trying to cut costs and unload massive debt following years of high fuel prices and labor struggles. The airline also announced that CEO Gerard Arpey stepped down and was replaced by Thomas W. Horton.

"This was a difficult decision, but it is the necessary and right path for us to take … to become a more efficient, financially stronger and competitive airline," Horton said in a statement.

AMR was the only major U.S. legacy carrier that did not file for bankruptcy protection after the Sept. 11 attacks, which caused a deep slump in the industry.

The airline on Tuesday stressed it would continue to operate flights, honor tickets and take reservations. But Horton said American will likely reduce flight schedules "modestly" as it goes through restructuring.

American officials said the AAdvantage frequent-flier program and Admirals Clubs will be conducting "business as usual."

Bankruptcy filings allowed American's competitors to shed labor contracts, unburden themselves of debt and start making money again. American was stuck with higher costs, and had to match its competitors' lower fares or lose money.

American Captain Dave Bates, president of the Allied Pilots Association, told union members Tuesday that the bankruptcy filing "was not entirely unexpected" and expressed disappointment "that we find ourselves working for an airline that has lost its way."

Other airlines also grew by pursuing acquisitions and expanding overseas. American was the biggest airline in the world in 2008, but it has been surpassed by United, which combined with Continental, and Delta, which combined with Northwest.

Delta was the last major airline to file for bankruptcy protection, in 2005.

The AMR bankruptcy may prepare the runway for a merger with US Airways Group Inc. as the two seek to become more competitive on size and costs, analysts said.

"American potentially needs a partner to achieve more scale," Kevin Crissey, an analyst with UBS Securities LLC in New York, wrote in a note Tuesday. US Airways, based in Tempe, Ariz., "may provide that avenue."

US Airways, the fifth-largest U.S. carrier, failed in a 2006 hostile bid for Delta Air Lines Inc. and in two rounds of merger talks with United Airlines. And the airline has said it remains interested in a merger.

American and US Airways spokesmen declined to comment.

TWA LEGACY

When AMR acquired TWA's assets more than a decade ago, it resulted in the nation's largest airline at that time. Prior to that, TWA had declared bankruptcy three times in less than 10 years.

"It is always disappointing any time a company has to file for bankruptcy," said Hamm-Niebruegge, who worked at TWA. "It is a hard thing to go through as an employee."

When American took over, it maintained much of the St. Louis flight schedule. But its presence eroded after the Sept. 11 terrorist attacks sent the commercial aviation industry into a tailspin that continued through the latest recession.

Today, American's mainline planes account for roughly 18 percent of the available seats from Lambert, Hamm-Niebruegge said. By comparison, Southwest Airlines has 86 departures accounting for 44 percent of available seats.

American offers daily flights from St. Louis to Chicago O'Hare, Dallas-Fort Worth, Miami, New York, Los Angeles and Washington.

Because Lambert is served by 13 carriers, she added, it was better able to weather recent consolidations, and AMR's bankruptcy filing should be no different.

Officials at Kansas City International Airport say it is too soon to know how bankruptcy will affect American's obligation to pay $1.1 million a year in rental payments for a portion of an aircraft overhaul base at the airport. American vacated the facility, where it had repaired planes, last December.

David Long, deputy director of aviation in charge of properties and commercial development at Kansas City International, said American's rental obligation runs through Dec. 31, 2029.

That obligation, which escalates in the outer years, can be reduced if tenants are found for a portion of the overhaul base that was originally designed to accommodate Concorde supersonic jets TWA once considered for its fleet.

"We did have a conversation with AMR, and nothing has been decided," he said.

Landing tenants for the overhaul base — which once housed 400 airline employees — has become a focus of an aggressive economic development effort. To date, Long said, the city is close to replacing those jobs with tenants housed in other parts of the base.

In a filing with federal bankruptcy court in New York, AMR said it had $29.6 billion in debt and $24.7 billion in assets.

In addition to reducing the flight schedule, Horton said there would probably be corresponding job cuts at American. The airline has about 78,000 employees and serves 240,000 passengers per day.

The prospect of workforce reductions has an all-too-familiar ring to some American employees.

Former TWA flight attendants have spent years trying to regain their careers after being effectively stapled to the bottom of the seniority list covering the combined workforce following the TWA acquisition.

Roughly 1,000 former TWA flight attendants have been recalled during the past year, leaving about 220 on the recall list, former TWA flight attendants say. Now this news.

"It's kind of heartbreaking in a way," said Gretchen Boardman, a retired flight attendant for TWA and American, and a spokeswoman for the Coalition for Union Principles.

Former TWA flight attendant Carol Samuelson has been furloughed twice since the two airlines were joined in 2001. She just got recalled by American last December and finally worked her way back to St. Louis.

"We don't know if this means another furlough," she said. "At TWA, we went through many bankruptcies and didn't get furloughed every time."

The Associated Press and Bloomberg News contributed to this report.