AIRCRAFT assembly workers walked out on strike on Friday at Boeing factories near Seattle after union members voted overwhelmingly to go on strike.

The workers rejected a tentative contract that would have increased wages by 25 per cent over four years.

Members of the International Association of Machinists and Aerospace Workers (IAM) voted by 94.6 per cent to reject the proposed contract and 96 per cent to approve a strike.

The strike involves 33,000 Boeing machinists, most of them in Washington state, and is expected to shut down production of the company’s best-selling airline planes. 

The striking machinists assemble the 737 Max, Boeing’s best-selling airliner, along with the 777, or “triple-seven” jet, and the 767 cargo plane at factories in Renton and Everett, Washington. 

The machinists make the equivalent of about £57,000 per year on average, not counting overtime, and that would rise to about £81 at the end of the four-year contract, according to Boeing.

But the deal fell short of the union’s initial demand for pay raises of 40 per cent over three years. The union also wanted to restore traditional pensions that were axed a decade ago but settled for an increase in Boeing contributions to employee’s retirement accounts.

Outside the Renton factory, people stood with signs reading, “Historic contract my ass” and “Have you seen the damn housing prices?”

Car horns honked and a boom box played songs such as Twisted Sister’s We’re Not Gonna Take It and Taylor Swift’s Look What You Made Me Do.

Boeing responded to the strike announcement by saying that it was “ready to get back to the table to reach a new agreement.

“The message was clear that the tentative agreement we reached with IAM leadership was not acceptable to the members.”

The company statement said: “We remain committed to resetting our relationship with our employees and the union.”

IAM District 751 president Jon Holden said that machinists were bitter about stagnant wages and concessions they have made since 2008 on pensions and healthcare to prevent the company from moving jobs elsewhere.

“This is about respect, this is about the past and this is about fighting for our future,” Mr Holden said in announcing the strike.

The vote also was a setback to Mr Holden and union negotiators, who recommended workers approve the contract offer. 

Mr Holden, who had predicted workers would vote to strike, said that the union would survey members to decide which issues they want to stress when negotiations resume.