"That's why our proposal to move future hires to an enhanced 401(k)-style retirement plan is so important, as we have repeatedly emphasized over the course of these negotiations."
Washington Gov. Jay Inslee said he's concerned about the split vote and spoke to union and Boeing representatives, urging them to resume negotiations.
"We cannot overstate the importance of the aerospace industry to the economy of Washington," Inslee said in a statement. "There are more than 131,000 employees in aerospace-related companies working across the state, the vast majority of which are directly reliant on the Boeing Company."
The union's nearly 23,000 employees are mostly in the Puget Sound region.
The factory-floor assembly work is done by the members of the International Association of Machinists. The Machinists approved a new, four-year contract in December 2011.