(Reuters) - Boeing's ( BA ) Washington state factory workers will vote on Wednesday on whether to give their union a strike mandate as they seek a 40% raise in their first full negotiation with the planemaker in 16 years.

Many of the estimated 30,000 workers who build Boeing's ( BA ) 737 MAX and other jets will rally in support of a mandate at Seattle's T-Mobile Park, although they cannot strike before their contract expires on Sept. 12. 

While the vote is considered procedural, the union is kicking off the 12 p.m. PDT event with fanfare, including an earlier convoy of workers on 800 motorcycles. 

"It does empower the negotiating committee, it does send a strong message," union local president Jon Holden said about the vote during a June interview.  

For example, the vote would free up funds in case members choose to strike later, he added. 

North American unions have capitalized on tight labor markets to win hefty contracts at the bargaining table, with airline pilots, autoworkers and others scoring big raises.

But Boeing ( BA ) has lost ground to rival Airbus as it navigates a crisis that erupted after a door plug blew off an Alaska Airlines 737 MAX jet in mid-air on Jan. 5.

The planemaker recently said it would plead guilty to criminal fraud conspiracy to resolve a U.S. Justice Department investigation linked to two 737 MAX crashes from 2018 and 2019 that killed a combined 346 people, the government said in a court filing earlier this month. 

The U.S. planemaker, which has announced a deal to acquire key supplier Spirit AeroSystems for $4.7 billion, is expected to burn rather than generate cash in 2024.

"We remain confident we can reach a deal that balances the needs of our employees and the business realities we face as a company," Boeing ( BA ) said in a statement.

   The International Association of Machinists and Aerospace Workers (IAM), which represents the Boeing ( BA ) workers, has said the company's financial and production challenges will not change its workers' readiness to strike if needed. 

"Knowing our relationship here with the Boeing Co ( BA ) and how things have been, our members are ready to strike," Holden told Reuters. 

He said workers have already been holding sporadic rallies in the factories and there would be more demonstrations expected in late August.  

Boeing ( BA ) has more than 66,000 employees who live and work in Washington state on programs like the MAX, 767 and 777 widebody jets, representing the largest percentage of the company's global workforce.