ARLINGTON, Va. - US Airways has assured customers they won't notice any changes following its decision to file for bankruptcy protection, the second time in two years the airline has sought such help as it struggles against lower-cost rivals.

The filing Sunday in U.S. Bankruptcy Court in Alexandria came after US Airways was unable to obtain $800 million in annual cost cuts from its workers' unions that the airline said it needed to stay afloat. A hearing was scheduled today.

"We have come too far and accomplished too much to simply stop the process and not succeed," said Bruce Lakefield, US Airways' president and chief executive. "A restructured US Airways with low costs and low fares will be a dynamic competitor."

The company, the nation's seventh-largest airline, said financial deadlines looming Sept. 30 forced it to file now to conserve cash to navigate bankruptcy. The airline also had a $110 million pension payment due Wednesday if it had not sought protection.

US Airways Chairman David Bronner had warned several weeks ago that the airline would most likely have to liquidate if it filed for bankruptcy. Lakefield backed off those comments Sunday and assured customers that the airline faced no immediate danger of shutting down.Customers were pleased - yet wary."I would not be very happy if they closed down," said Peter Windeit, who regularly flies to U.S. cities and to Europe on business. "I hope they get the money to get out of this."The company's return to bankruptcy comes as several of its larger rivals also confront weak finances. UAL Corp.'s United Airlines has been operating under bankruptcy for nearly two years, AMR Corp.'s American Airlines was on the brink of a filing 18 months ago, and Delta Air Lines Inc. warned it might seek protection soon if it cannot trim its labor costs.US Airways' bankruptcy filing could cost federal taxpayers. The government loaned the airline $900 million last year as part of a special program to assist airlines after the 2001 terror attacks and the airline still owes Uncle Sam $718 million.US Airways said Sunday it has an agreement in place with the government and with other lenders to use some of its cash reserves to continue operations while in bankruptcy. In its filing, the company listed $8.8 billion in assets, including $1.45 billion in cash and $8.7 billion in liabilities.Last Monday, a deeply divided pilots union refused to allow its membership to vote on a company proposal that would have cut pay by 20 percent and retirement plan contributions by 50 percent.As recently as Friday, US Airways made a last-ditch effort to reach a deal with the pilots, offering a proposal with minimum pay cuts that would have required more flight hours each month.When US Airways first filed for bankruptcy in August 2002, investment firm Texas Pacific Group had already agreed to invest $200 million in the airline. That plan was supplanted by the Retirement Systems of Alabama, a pension fund for state workers, which invested $240 million. Bronner acknowledged the Alabama fund could lose its entire investment, which amounts to less than 1 percent of the fund's portfolio.US Airways actually turned a small profit - $34 million - in the last quarter. But the April-June period is typically an airline's strongest, and its prospects appeared poor because of relatively high labor costs, expensive fuel costs and intense new competition from low-cost carriers.When US Airways emerged from its first bankruptcy in March 2003, the airline made numerous changes as it sought to become a low-fare carrier. It de-emphasized its hub-and-spoke system, eliminating its Pittsburgh hub altogether. It implemented a lower, simplified fare structure along parts of its network, including its hub in Philadelphia, where it faces a severe new challenge from Southwest Airlines.