NEW YORK (AP) — Boeing workers who build fighter jets are planning to go on strike Monday at midnight.

(Reuters) -Union members who assemble Boeing's fighter jets in the St. Louis area rejected the U.S. planemaker's latest contract offer on Sunday and will strike at midnight on Monday, the International Association of Machinists and Aerospace Workers union (IAM) said.

The union division that represents about 3,200 workers in Missouri and Illinois on Sunday rejected the aerospace giant’s latest four-year contract proposal, scheduling a strike to begin at midnight Monday and threatening the company’s fragile turnaround effort.