The major players in a key industry file for bankruptcy protection with the hope of reshaping operations quickly and coming back to compete more strongly.

But it's not the automakers; it's the airlines, which just a few years ago underwent a wrenching restructuring in bankruptcy court that fundamentally altered the travel industry.

Circumstances are different. But with Chrysler's filing for bankruptcy protection Thursday, and General Motors Corp. flirting with that same option, the experience of the airlines could offer useful lessons.

Air travel, for example, was largely unaffected by the spate of carrier bankruptcies that followed the Sept. 11, 2001, terrorist attacks — which may be reassuring for car buyers, especially those worried about warranties not being honored.

Richard Gritta, a professor of finance at University of Portland in Oregon who has studied automakers and airlines, said the similarities between the two industries have been remarkable.

The auto business has been "marked by bad operational management that didn't realize that the Japanese and then later the Koreans were making better cars. They didn't pay attention and that's when debt started to pile up," Gritta said. "Toward the end, they have become like the airlines."

Since 2002, three of the four largest airlines have been in bankruptcy court: United Airlines, Delta Air Lines and Northwest Airlines. Hawaiian Airlines filed for bankruptcy in March 2003, and emerged two years later.

The exception was American Airlines. Among U.S. automakers, that same role may fall to Ford, which says it won't accept government bailout money and appears at no risk of failing.

Like the automakers, the airlines were suffering from high labor costs and increased competition.

By filing for Chapter 11, the airlines got the chance to do things that they would not have been able to do outside bankruptcy court, including forcing employees to accept lower pay and benefits, getting aircraft leases reduced and eliminating debt.

They also got out from under the burden of employee pensions that cost them billions of dollars a year.

As a result, carriers that reorganized under Chapter 11 have been able to weather some of the toughest business environments in decades, including last year's fuel hikes and this year's travel downturn.

Delta and Northwest, previously the third- and fourth-largest in terms of passenger traffic, restructured operations in bankruptcy and Delta quickly acquired Northwest, supplanting American as the world's largest carrier.

"American is at a disadvantage compared to most of the other carriers that went through bankruptcy," said Ray Neidl, a longtime New York airline analyst. "Others were able to get their cost structures down far more than American."

Workers at American agreed to $1.8 billion in payroll cuts, pushing compensation to levels of a decade earlier. But many of its rivals were able to make significantly larger cuts.