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.

Boeing workers who build fighter jets went on strike Monday at midnight Central Daylight Time. About 3,200 workers at Boeing facilities in St. Louis; St. Charles, Missouri; and Mascoutah, Illinois, voted to reject a modified four-year labor agreement with Boeing, the International Association of Machinists and Aerospace Workers union said Sunday.

Some 3,200 Boeing workers who build fighter jets in St. Louis and another Missouri site and one in Illinois are on strike, their union says.