More than 3,200 union members who assemble Boeing's fighter jets in the St. Louis area and Illinois went on strike on Monday after rejecting a second contract offer the previous day.

About 3,200 machinists in St. Louis walk off the job after failing to reach an agreement on wages and retirement benefits.

Boeing warned over the weekend that it anticipated the strike after workers rejected its latest offer, which did not further boost the proposed wage hike.