SEATTLE — Boeing Co. aircraft assembly workers voted overwhelmingly to strike for the second time in three years but union leaders agreed to hold off on the walkout for 48 hours at the request of Washington Gov. Chris Gregoire and a federal mediator. The vote late Wednesday was 87 percent in favor of a strike that was to have begun at 12:01 a.m. PDT Thursday, after the expiration of the old contract covering more than 27,000 workers. With the extension, Boeing spokesman Tim Healy said the two sides would meet with a federal mediator Thursday. In separate balloting, union members also voted 80 percent to reject Boeing's third three-year contract offer, which included pay raises averaging 11 percent. The offer, which Boeing described as its "best and final," included bonuses totaling at least $5,000, raises averaging 11 percent, pension increases and a 3 percent cost-of-living adjustment _ $34,000 in average pay and benefit gains per employee, according to the company. Announcement of the 48-hour extension at the machinists union hall drew booing and shouting from about 100 angry shop stewards and other activists that frequently made it impossible for Mark Blondin, the union's chief negotiator, and Tom Wroblewski, president of Machinists District Lodge 751, to be heard. "We have told you all along that our job as negotiators is to negotiate a contract that is acceptable to you, not to negotiate a strike," Blondin said. When the shout ...