Boeing's 18,000-strong machinists union voted overwhelmingly on Thursday to strike effective at the stroke of midnight (7am GMT yesterday), according to the union Web site.
Members of the International Association of Machinists (IAM) voted 86 percent in favor of taking to the picket lines instead of showing up for their Boeing jobs in the Seattle, Portland area, and Wichita, Kansas, the union reported late on Thursday.
The IAM contract covering workers in the Seattle, Portland area, and Wichita, Kansas, was set to expire early yesterday.
In authorizing the strike, IAM members rejected Boeing's "last-best" contract offer.
"We are disappointed with the outcome of the IAM vote today," Boeing said in a written release.
"No one ever benefits from a strike," the company said.
Boeing asked employees not represented by the union to show up at their jobs as usual, saying those willing to keep working would be "afforded the opportunity to do so for as long as there is meaningful work to perform."
"We don't intend to assemble airplanes during this strike," Boeing said in its statement.
The company said it will focus on supporting in-service fleets of customers and design and development activities during the strike.
Union leaders had urged members to reject the contract and to authorize a strike, claiming the aerospace firm was asking for too many givebacks.
"Boeing insists you make concessions while the top executives continue to collect millions and give up nothing," IAM Local 751 told its members on its Web site.
Boeing countered that its offer "compared favorably" with others in the industry.
In the last round of negotiations in 2002, a majority of members rejected the contract, but the strike vote fell short and the contract was put in place.
Boeing spokesman Chaz Bickers said the company had plans in place in the event of a strike, but he declined to elaborate on what might be in store. There are no plans to replace striking workers, Boeing said.
Boeing offered workers two lump sum bonuses totaling US$6,000, as part of a package of up to US$15,400 in additional wages, bonuses and incentive pay.
A key issue was pensions, with the company offering a US$66-a-month payment for each year a worker was employed at the company. But that level fell short of what the IAM wanted.