E mployees at Boeing’s St. Louis defense factories rejected a contract offered by the aerospace giant Sunday afternoon and around 3,200 workers began striking starting at midnight—the first walk out the company has faced at its St. Louis defense hub since 1996.

Despite a six-figure pay offer and bonuses on the table, workers from Boeing say this fight is about more than money.

Roughly 3,200 workers are striking at sites in Missouri and Illinois. Members of the labor union representing the workers rejected a modified contract offered by Boeing last week.