The union leaders of the Society for Professional Engineering Employees in Aerospace are recommending their members vote no on Boeing’s contract offer.

Leaders of SPEEA, which has 23,000 members, said Boeing’s four-year contract offers includes the lowest wage pools since 1975 at a time the company is doing well.

Boeing said the offer is competitive and that engineers and technical workers are paid above the national average.

Boeing also said it could move work out of state if costs escalate.

SPEEA members have staged demonstrations and work slowdowns, doing only what their current contract requires.

The deadline to vote on Boeing’s contract offer is 5 p.m. Monday, when the ballots will be counted.

If union members reject the contract offer, a strike vote could come later.