The Boeing Co" href="http://topics.nytimes.com/top/news/business/companies/boeing_company/index.html?inline=nyt-org">Boeing Company, whose order books are bulging with demand for its planes, was hit by its second major strike in three years early Saturday, when the union that represents 27,000 machinists in Washington State, Oregon and Kansas walked off the job.

The union, the International Association of Machinists and Aerospace Workers, said its members struck at 3:01 a.m. Eastern time after last-minute talks failed to bring an accord. No new talks were scheduled.

Boeing said its plants would remain open during the strike and employees who were not members of the machinists union were expected to come to work. The company said it would build airplanes during the walkout.

Talks broke down over a variety of issues, including pay, pensions and job security.

Workers began to walk picket lines as soon as the strike was called, although its impact would not be fully felt until Monday.

The strike was Boeing’s second in its last two sets of contract talks and the seventh since 1948, when historic showdown Boeing workers spent a month on strike in 2005.

The latest walkout came after Boeing and the union failed to reach agreement on a new three-year contract during negotiations in Orlando, Fla., that were supervised by a federal mediator. Boeing Commercial AirplanesThe union agreed to extend its contract 48 hours late Wednesday.

The president of Boeing Commercial Airplanes, Scott E. Carson, said in a statement: “The differences were too great to close.”

Boeing has a backlog of more than 3,600 orders valued at $263 billion in all. The majority of those aircraft are versions of the Boeing 737, a short-range plane that is the world’s most popular.

Boeing could easily withstand a short strike. But a long walkout could cause more delays in the development of the Boeing 787, a long-range jet nicknamed the Dreamliner.

The Dreamliner is meant to be significantly more fuel-efficient than the Boeing 747. But the Dreamliner has encountered problems, which have pushed back its delivery date more than a year.

“Talks with the Boeing Company did not address our issues,” the union’s district president, Tom Wroblewski, told members in an e-mail message. When the union agreed Wednesday to extend its contract, workers had already voted 87 percent in favor of a strike and 80 percent against Boeing’s last contract offer.