Boeing Co. machinists soundly rejected a new labor contract on Wednesday that would have let them build the company's newest jetliner in Washington, a historic decision that could forever alter the course of Boeing's 97-year presence in the state.

The 31,000 International Association of Machinists members voted by a 67 percent margin against a deal that would secure an estimated 20 years of work building Boeing's 777X jet, but that would have terminated their pension plan and raised their healthcare costs.