Boeing engineers and technical workers, represented by the Society of Professional Engineering Employees in Aerospace, rejected a proposed four-year contract offer on Friday.
Union members voted down the proposal, stating that the guaranteed wage increase in the contract would be outpaced by inflation. In addition to rejecting the offer, the members authorized the union's negotiation team to pursue a strike.
A potential strike may occur if a new agreement is not reached by October.
This development sets the stage for a challenging period for the US planemaker, which is currently in the final stages of certification for crucial aircraft models.