Sara Dela Cruz, 29, a flight attendant at United Airlines for six years who regularly flies from Boston to California for the airline, lost seven friends on Sept. 11, 2001, when two United jets were commandeered and crashed in suicide attacks on New York and the Pentagon.

She keeps photos of some of those co-workers on her desk at the flight attendants union office near O'Hare International Airport, and she looks at their pictures frequently. It's not just for sentimental reasons, but because it serves to remind her what United's workers are fighting for now: the survival of the airline, which filed for bankruptcy protection Dec. 9, citing $20 million a day in losses.

"I have this feeling of patriotism," said Dela Cruz, who recognizes that layoffs and pay cuts are looming for the airline's 80,000 workers, including 3,000 in the Washington area. "We cannot let United fail. It would play right into what the terrorists had planned for us."

Two weeks after the Chapter 11 bankruptcy filing, workers at United Airlines are deeply worried about the future of the airline where many have spent decades of their lives. While some are rushing to retire or looking for other jobs, many others, like Dela Cruz, said they are committed to helping ensure the airline's future, despite the potential cost to themselves, and even though many believe the airline fell victim as much to past management mistakes as to terrorism.

In its bankruptcy filing, United said the company would have to "substantially" cut pay and change work rules to become profitable again. The company is also drawing a firm line in the sand with its workers by pressing forward to file a legal document, called a 1113 motion, that would allow it, if necessary, to erase its collective-bargaining agreements with unions, some forged over decades of negotiation. The company has stressed that the filing is mainly procedural at this point, but it places pressure on workers to accept changes they might otherwise resist.

Further negotiations will begin after Christmas, with union officials expecting they will need to reach acceptable compromises by mid-January. The tone at this point remains conciliatory, though the coming weeks may bring tough negotiations. "This is uncharted territory for us," said United spokesman Jeff Green. "We've never been down the Chapter 11 road before."

United Airlines prospered during the era of government regulation but began foundering, along with other older airlines, after the industry was deregulated in 1978. The older airlines have been battered by low-cost competitors that compete more nimbly in the marketplace, serve fewer rural, less-lucrative communities, and lack the salaries and benefit packages that were fostered during the years of government protection. Then, ticket prices rose as operating costs increased. But with Internet-based price-cutting widespread, it has become more difficult for many airlines, including United, to compete, particularly after travel volume dropped off in the past two years. United was facing financial trouble even before the terrorists struck.

Many older workers with high seniority are considering retiring at the end of the year, union officials said. In New Orleans, where there are 48 machinists in the union, nine have requested retirement papers. In Philadelphia, about 20 of 70 members plan to retire.

In Des Plaines, Ill., at a one-story stucco union-lodge with an American flag flying at the entrance, about 100 machinists attended an informational meeting Thursday night led by union officials who explained potential changes in pension benefits. About a dozen employees clutched retirement application forms they wanted to review with union officials. Union officials said 94 workers, out of 5,000 members based there, have said they plan to retire now.

Karen Asuncion, a machinists union official, said some workers are retiring quickly to protect pension benefits they hope will be grandfathered under earlier agreements. They fear that United's financial problems will cause the company to reduce the level of benefits for future retirees.

Dave Willy, 55, of Fox Lake, Ill., who has worked at United for 36 years in ramp service, said he will retire within the week -- a decision he said he wishes he did not have to make.

"I wasn't going to go, but to keep what I've got now, I've got to go," he said. "This could impact my life for a long time."

Michael Peat, a machinists union official, said the retirements are helping to make younger workers' jobs safer because the company will need to lay off fewer workers. "That will relieve some of the pressure," he said.

United's management said it is losing executive-level workers as well. In a bankruptcy filing, the company asked to be permitted to spend up to $107 million for retention bonuses to keep key workers who might otherwise jump ship.

However, many workers said they intend to stick it out with United and hope for the best. Some said they hope the company's new chief executive, Glenn F. Tilton, will "come in swinging" and lay off some of the managers who they said have created problems in the past. But they said they are willing to take some hits as well.

"The unions have to be responsible, too," said Ray Prost, 61, a ramp employee and union activist who has worked for United for 37 years. "Some jobs will have to be re-evaluated."

Many United workers worried aloud about how they might handle a significant pay cut. Some can handle a pay reduction more easily than others. While pilots earn an average of about $190,000 a year, excluding benefits, and mechanics earn about $76,000, passenger service workers earn about $42,000 and flight attendants earn about $41,000, according to figures compiled by the Association of Flight Attendants.

Franko Ocasio, a flight attendant with United since 1995, said he has had a hard time grasping the extent of United's financial woes. He left Continental Airlines, which went through bankruptcy twice, to join United, partially because of the firm's record of stability.

"I never thought it would get to this point -- this is United, after all," Ocasio said. "It wasn't supposed to happen here."

And now he worries about how he will maintain his standard of living if pay cuts come. Ocasio, who earns $34,000 a year, is based in New York but has only been able to afford to live there since May. He now has a studio apartment in the Bronx that rents for $700 a month. He said he has been told he might have to accept a 10 percent pay cut, which he said would require him to take a second job to make ends meet.

Dela Cruz, the flight attendant who lost friends on Sept. 11, said she could suffer financially, too. But, she said, she was "even more committed because of the things we might lose."

"It's bigger than a job," Dela Cruz said. "It's 70 years of airline history."

"I never thought it would get to this point -- this is United, after all," flight attendant Franko Ocasio said. "It wasn't supposed to happen here." He joined United partially because of its record of stability.