Several thousand workers at three Midwest manufacturing plants where Boeing develops military aircraft and weapons went on strike early Monday, potentially complicating the aerospace company's progress in regaining its financial footing.

Boeing is being hit with its second strike in less than a year after 3,200 hourly workers walked off their jobs building military aircraft.

More than 3,200 workers at Boeing defense factories walked off the job Monday. Members of the International Association of Machinists voted overwhelmingly to reject a tentative agreement that would have given union members a 20% pay increase over the next four years.