Nearly a week after 4,400 mechanics and aircraft custodians walked off the job at Northwest Airlines Corp., the airline said its operations were steadily improving.

"We have run a reliable airline. We have met our customers' needs," Douglas M. Steenland, Northwest's president and chief executive, said in an interview yesterday. "That was our goal, and we met our goal in that regard."

At the same time, Northwest executives said that because of increased fuel prices, the $1.1 billion it was seeking from its workers is now too little and that the airline may have to increase its sought-after target.

"We are looking at that request in the light of the changes of the fuel prices. We have made no decisions but simply looking at it," Steenland said.

It was those concession targets that sent members of the Aircraft Mechanics Fraternal Association, which represents the airline's mechanics and aircraft cleaners, onto the picket lines last week in the nation's first major airline labor action since 1998. The mechanics rejected Northwest's demand for $176 million in pay and benefits cuts. The mechanics said the move would have resulted in a 25 percent pay cut and eliminated more than 2,000 jobs.

This spring, Northwest, the nation's fourth-largest airline, said it would need $1.1 billion in annual concessions from its unions. At that time, crude oil prices were in the mid-$40-a-barrel range. This week, oil prices hovered around $68 a barrel. The increase represents an extra $900 million a year in jet fuel costs for Northwest.

As Northwest's executives spent the past week seeking to minimize the strike's interruptions to service, the airline was also trying to determine how much more in concessions it may need from its workers. In December, Northwest's pilots agreed to $265 million in annual pay and benefit cuts. The airline also was seeking about $107 million from its baggage handlers and ground workers and $143 million from its flight attendants.

If the airline cannot obtain the cuts, Steenland reiterated, it may be forced into filing for Chapter 11 bankruptcy protection. "That's clearly one of the things that we have to look at," he said.

Last Saturday, as Northwest's mechanics took to the picket lines, the airline immediately replaced them with about 1,300 former airline workers and managers. That move, labor watchers said, would have ramifications for future airline labor negotiations.

Steenland said Northwest's dispute should not be seen as a barometer for future labor relations. "This is not a paradigm shift," he said. "This doesn't say anything about the swing in power between management and labor. This is a circumstance that pertains to the nature of negotiations between Northwest and one of its unions. It doesn't indicate a pattern or precedent that is likely to continue with other unions."

Yesterday, Northwest officials said the airline completed 98.2 percent of its flights. That's up from 91.6 percent of flights completed Aug. 19, the day before the strike began. Northwest attributed the better performance to being able to reduce the number of aircraft out of service because of maintenance problems to 17, down from 57 on the eve of the strike, said Andy Roberts, executive vice president of Northwest's operations.

"We are pleased with the results as we think a (more than) 90 percent completion factor during a strike is very impressive," said Merrill Lynch & Co. analyst Michael Linenberg.

Still, the airline said a little more than half of its flights arrived on time yesterday. That was largely because of thunderstorms in the Midwest, Roberts said.

Meanwhile, some members of the mechanics union said they are increasingly frustrated with the stance their leaders have taken.

Bob Lemire, 64, who has worked as a Northwest mechanic for 16 years, said the members should have had a vote on the contract offer, even if the vote was against the proposed agreement. Lemire said that the members might have agreed to concessions for this contract and, when Northwest was financially stable again, renegotiated for a better agreement.

"This contract had a good enough chance of getting through," he said. Lemire, who worked as a mechanic for Eastern Air Lines Inc. for 26 years until it went out of business in 1991, said he was disappointed at the outcome of the failed talks.

"What has happened is beyond belief. Look at where we are now. We're sitting here with nothing," Lemire said.

Northwest's Roberts said about five mechanics have crossed the picket line and returned to work.

O.V. Delle-Femine, national director of the machinists union, said that 93 percent of members voted to authorize the strike and that a majority of members support the strike. He said copies of Northwest's proposed contract had been distributed to members.

"We would have been crucified if we had brought that junk back to the members," Delle-Femine said. "I heard from a couple who were upset, but the majority of the guys said we did a great job not taking (the contract)."

Meanwhile, at Detroit Metropolitan Airport, Northwest's largest center of operations, there were signs that some of Northwest's flight attendants were supporting their striking colleagues, at least tacitly. A flight attendant cheered up the circling crowd of striking mechanics by serving cookies.

Some travelers who have flown Northwest during the past week said they have not noticed any difference in service. Dave Sharpy, a Seattle-based regional director for a health care consortium, flew to Honolulu on Sunday, the strike's second day, and said he had no problems with his flight.

A Detroit native whose father was a member of the firefighters union there, he said he had "little concern" about crossing a picket line. "At some point both sides have to come together and talk things out. But honestly, I don't really care one way or another," he said.

Alexander reported from Washington; Joyce reported from Detroit.

Steve McKeon, a Northwest Airlines mechanics union striker, at Minneapolis-St. Paul International Airport. Strikers have been at posts around the airport since Aug. 20.

A replacement mechanic checks a Northwest Airlines jet at Detroit Metropolitan Airport. The mechanics union has been on strike since Aug. 20.