Workers said a main reason for rejecting the contract was that the wage increase was far short of what they wanted.

Boeing stock was falling after investors were handed yet another thing to worry about. A key International Association of Machinists and Aerospace (IAM) Workers Union local representing some 33,000 Boeing workers voted down a new four-year labor deal with the airplane maker.

The vote sets the stage for a massive 33,000-person strike across the jet maker’s commercial production lines.