Northwest Airlines Corp. encountered picket lines and some flight delays as it weathered the first day of a strike by its 4,400 mechanics and maintenance workers.

The first major airline strike in seven years has set the stage for a confrontation that could reshape labor relations in a struggling industry. The airline unions, once a dominant force, have lost much of their power as their members have had to sacrifice wages and jobs repeatedly to keep the carriers afloat. With the industry in dire condition, the balance of power appears to be shifting away from organized labor to airline executives.

Northwest was able to maintain operations largely because its other labor groups, representing pilots, flight attendants and baggage handlers, ignored the strikers and reported to work.

Airline officials claimed victory yesterday, saying 14 months of preparations for the walkout were paying off. They added that no further negotiations with the union were planned.

"We're predominately running on schedule," said Andrew C. Roberts, Northwest's vice president of operations. "We don't expect any delays to increase, and our operations should improve over time."

But smooth operations in the morning turned bumpy. A flight from Detroit to Boston scheduled to depart at 10:30 a.m. left at 4:39 p.m. because of mechanical problems. Another Detroit-to-Boston flight was delayed nearly an hour because of a problem loading luggage. A New York-to-Tokyo flight with a departure at 2:35 p.m. was rescheduled to leave at 5:30 p.m. because of an "aircraft change due to maintenance," according to the airline. And four tires blew out on a jet landing in Detroit in what the airline described as a braking issue unrelated to the strike. No one was injured.

The disruptions were not on the scale of previous walkouts. In the past, sympathetic unions commonly sided with their fellow employees and launched slowdowns or strikes of their own. Now, many union workers prefer to preserve their jobs at lower wages than risk losing them through labor strife.

In earlier days, airlines also risked an exodus of travelers reluctant to cross picket lines and concerned about disruptions to flight schedules, boosting the workers' negotiating power. But those forces were not materializing yesterday.

In Miami, Alice Hill, 59, an aircraft hardware salesperson on her way back to Los Angeles from a seven-day Caribbean cruise with her family, said they had not experienced any problems.

"The airline told us before we left not to believe all the hoopla about delays and cancellations that we were hearing on the news. They said they would finish out all the flights on the first day of the strike," Hill said. "I'm not honoring any strike. I didn't honor the grocery strike in L.A., and that was three months. My family still gets hungry. My mission is to get [myself] on an airplane as fast as I can."

Northwest prepared for the walkout by lining up 1,300 replacement mechanics, mostly workers laid off from other airlines who were willing to work for lower wages. It also arranged for lower-paid contract workers to perform other jobs such as aircraft cleaning.

Industry observers said Northwest's challenge in coming days will be to ensure that the newly hired workforce operates at a high level. "We'll know in the next 72 hours," said Michael J. Boyd, a consultant with Boyd Group, based outside Denver. "This is machinery. Machinery breaks. Just how efficiently this new maintenance team can handle the day-to-day operations will be pretty much known by then."

As the strike loomed, the carrier cut about 448 flights, or about 15 percent of its Saturday schedule, in an early launch of its fall schedule. Airlines traditionally cut the number of flights in the fall after the peak summer travel season. Northwest had intended to start its fall schedule on Aug. 27.

The walkout, which began early Saturday morning, was the first major labor action against a large U.S. airline since 1998, when Northwest's pilots walked off the job for nearly three weeks.

At Reagan National Airport yesterday, Northwest passenger Meg Brown stood in line to check her luggage onto her flight to Wisconsin. Her mother, Judy Brown, a former flight attendant with the defunct Pan American World Airways and a former Teamster member, did not hesitate to cross the 10-person picket line outside the airport.

"We're flying no matter what," she said. "I know it's very hard on the employees at every level. But there's a need to restructure." Noting her union background, she added that she is "mindful" of the hardships. "This is a choice between two bad alternatives," she said.

Some travelers did side with the strikers. John Brodkin of Silver Spring said he was planning to fly on Northwest to Calgary, Alberta, next week but changed his booking to a flight that was less convenient.

"I do not wish to help Northwest break its unions, and I refuse to use any business that employs scab labor," Brodkin said.

Northwest, the nation's fourth-largest carrier, has said it has lost more than $3.6 billion since 2001 and is on the brink of filing for bankruptcy protection. The airline had sought $176 million in concessions from the mechanics as part of its efforts to cut $1.1 billion in annual labor expenses. The union said the airline wanted to slice the mechanics workforce in half by using more outside contractors and to cut the pay of remaining workers by 25 percent.

Northwest, which still has to obtain concessions from its pilots, flight attendants and baggage handlers, said the financial crisis of the airline and the airline industry in general precluded negotiating as it had in previous contract talks.

"We told them this were not negotiations as usual. Over the last four years, the marketplace has changed. We need a new labor structure to survive," said Julie Showers, Northwest's vice president of labor relations.

As part of the restructuring, airlines have moved much of their maintenance work to outside contractors. Oversight of the contractors by the Federal Aviation Administration has not kept up with the pace of outsourcing, according to the Department of Transportation's Office of Inspector General, raising some safety concerns.

Meanwhile, small groups of mechanics walked the picket lines. In Detroit, where Northwest is the largest carrier, dozens of Northwest mechanics picketed outside the airport. At Minneapolis-St. Paul International Airport, Northwest's hometown airport, demonstrations were described by one traveler as "surprisingly quiet and low-key." But in cities where Northwest has fewer flights, picketers were also far fewer. In Miami, only one mechanic was demonstrating early in the day, while at National Airport, about 10 picketers showed up.

The mechanics, many of whom have worked for Northwest for about 25 years, said they know they could lose their jobs permanently by striking. But they said they would rather fight.

"Our members know what's at stake. But half of our guys will lose their jobs if we sign" Northwest's proposed contract, said Steve MacFarlane, a spokesman for the union. "How do you sign a deal that betrays and sends half of your friends and family on the streets? Either we all stay or we all go."

Staff writer Catharine Skipp contributed to this report.

Dennis Koutsky, who has worked at Northwest for 26 years, holds his picket sign at a Northwest plane. Members of Northwest's Aircraft Mechanics Fraternal Association picket near the international terminal at Detroit Metropolitan Airport.