Delta Air Lines Inc. could file for Chapter 11 bankruptcy protection as soon as next week, a source familiar with the matter said yesterday.

Executives of the nation's third-largest airline spent the week meeting with lawyers and bankruptcy consultants.

Delta could file as early as Wednesday or Thursday, the source said. But the filing could be delayed if the airline is able to obtain $1 billion in pay and benefit cuts it has sought from pilots, the carrier's only unionized work group. Contract negotiations are to take place this weekend.

Even if the pilots agree on the concessions, a Chapter 11 filing is likely. "It's a crapshoot. A decision by the pilots could postpone it or we may go ahead and do it. It's that close," the source said.

Delta executives sent a message this week to the company's top frequent fliers, assuring them that even if the airline filed for Chapter 11 protection, tickets would be honored and its frequent-flier program would be unaffected.

Delta spokesman Anthony Black declined to comment on a Chapter 11 filing. He said the airline is working with its pilots and debt holders in an effort to reduce costs and avoid Chapter 11. "We're in a race against time," Black said.

Delta's filing would mean that three major U.S. airlines would be operating under Chapter 11 protection at the same time. That hasn't happened among the top 10 domestic airlines since 1992, when Continental, Trans World Airlines and America West were all operating under Chapter 11.

Arlington-based US Airways, the nation's No. 7 carrier in terms of revenue, filed for Chapter 11 protection last month for the second time in two years. United Airlines, the nation's second-largest carrier, has been operating under a court restructuring for nearly two years.

Yesterday, United agreed to hire Bridge Associates, an outside consultant to evaluate its business plan. The decision was reached as part of an agreement with United's mechanics and flight attendants, who had filed objections over the airline's reorganization plan with the bankruptcy court.

Traditional hub-and-spoke airlines such as Delta, United and US Airways will continue to struggle until they drastically cut their costs and flights, said airline analyst Ray Neidl of Calyon Securities. He said the industry continues to suffer from excess capacity, which has been exacerbated by the growth of low-cost carriers.

The traditional carriers are facing further difficulties in the traditionally weak travel seasons of the fourth and first quarters. Record high fuel prices also are weighing on the industry, as fuel is an airline's second-biggest cost after labor.

Even some low-cost, low-fare airlines are struggling. Dulles-based Independence Air, which launched this summer, filled less than half of its 50-seat regional jets in August and September. A report by airline analyst Robert N. Ashcroft of UBS Investment Research this week said the airline could face a Chapter 11 filing by January.

"There's too much competition," Neidl said. "The increased competition keeps the fares at record low levels, but the increased fuel prices are keeping the costs high."

Delta lost $646 million in the third quarter, sharply widening its loss of $164 million in the same period a year ago. It has racked up more than $6 billion in losses since 2001.

The airline ended the quarter with $1.45 billion in cash, about $550 million less than in the second quarter.

Delta shares closed Friday at $3.24, up 22 cents, or 7.28 percent. Before the Sept. 11, 2001, terrorist attacks, Delta shares were trading at around $41.

In a recorded telephone message to Delta pilots this week, Delta pilot spokesman Chris Renkel said union negotiators are scheduled to meet in Herndon on Monday for a briefing after the weekend talks.

"Your union leadership fully recognizes Delta's precarious financial situation. Much work has been done to date, but many issues remain unresolved," Renkel said.

Other airlines continue to report mounting losses. AMR Corp., the parent of American Airlines, the world's largest airline, reported this week a third-quarter loss of $214 million, compared with a profit of $1 million in the comparable quarter last year. The airline also warned its fourth-quarter loss would be "significantly wider" than the third quarter's because of continued high fuel prices in the typically weak winter season. AMR executives said the airline would launch a new round of efforts to cut costs and boost revenue, including furloughing up to 1,100 workers, reducing its fleet and trimming its domestic seat capacity by 5 percent starting in the first quarter. American also said it was adding seats to its planes, in effect eliminating its highly marketed "More Room Throughout Coach" campaign.