The strike started at Boeing facilities in St. Louis; St. Charles, Missouri; and Mascoutah, Illinois, after about 3,200 local members of the International Association of Machinists and Aerospace Workers voted Sunday to reject a modified four-year labor agreement, the union said.

A strike at Boeing's defense unit halts fighter jet assembly, including F-47 jet production, as 3,200 employees walk out over failed contract negotiations.

The strike involves roughly 3,200 workers at three Boeing sites, including its St. Louis hub, which is expected to be central to the F-47 program.