The threat of labor unrest follows last year’s two-month strike by a separate machinists union in Seattle, which disrupted Boeing’s ( BA) commercial jet production and prompted the company to raise $24 billion through an equity offering to offset the financial toll.

Boeing expects more than 3,200 union workers at three St. Louis-area plants that produce U.S. fighter jets to strike after they rejected a proposed contract

Union members who assemble Boeing’s fighter jets in the St. Louis area have “overwhelmingly voted” to reject the company’s contract offer on Sunday, with the company now preparing for an imminent strike.