Seattle ? The Boeing Co.’s largest union voted down a strike, its Machinist union-represented employees are reporting to work and operations in its commercial jet factories seem to be business as usual.

But labor troubles for the world’s largest producer of commercial jets are far from over.

As the contract talks with the Machinists wound to a close earlier this month, Chicago-based Boeing opened negotiations with its second-largest union, the Society of Professional Engineering Employees in Aerospace, which has some of the same contract priorities as the Machinist union. Contracts for three bargaining units of SPEEA, which represents engineers and technical workers, expire in early December. The union represents 19,000 workers with the majority in Seattle and Wichita.

Boeing also is awaiting arbitration on its practice of subcontracting work to outside companies, a move challenged by Machinists.

With lower commercial jet production and even deeper layoffs still a possibility, the company faces the lingering bitterness of Machinists who face three years of working under a contract they overwhelmingly rejected.

“Boeing management has challenges ahead,” said David Olson, a labor expert. “They have to be concerned about the morale of workers on the factory floor. They can do things that address the morale issue or they can ignore it which I think they would do at their peril. … If Boeing ignores this, their supposed victory will be a hollow one.”

The Machinists union, representing 25,000 production workers, mostly in commercial jet plants in Washington state, Wichita, Kan., and Portland, Ore., failed to muster the two-thirds majority needed to call a strike. Although 62 percent voted to reject Boeing’s “best and final” contract proposal on Friday, union bylaws require the membership to adopt the contract if the strike vote fails. It’s the first time the union has been unable to back up a contract rejection with a strike vote.

Boeing employs 12,500 workers at its Wichita plant. It is the state’s largest private employer.

For its part, the Machinists union said it plans to keep the pressure on Boeing and preserve as many jobs as it can.