Boeing factory workers voted to reject a contract offer and continue a more than five-week strike on Wednesday, in a blow to new CEO Kelly Ortberg's plan to shore up the finances of the struggling planemaker.

Boeing shares fell 2.7% in U.S. pre-market trading on Thursday after workers voted to extend a nearly six-week-old strike, throwing fresh uncertainty over the company's efforts to stabilize finances and restore its battered image.

Boeing’s machinists on Wednesday voted to reject a contract offer that would have ended their strike, which has now dragged on for more than a month. Roughly 33,000 members of the International Association of Machinists and Aerospace Workers Districts 751 and W24,