Boeing factory workers in the US voted against the company’s latest contract offer and remain on the picket lines six weeks into a strike that has stopped production of the aerospace giant’s best-selling jetliners.

Local union leaders in Seattle said 64% of members of the International Association of Machinists and Aerospace Workers who cast ballots on Wednesday voted against accepting the contract offer.

“After 10 years of sacrifices, we still have ground to make up, and we’re hopeful to do so by resuming negotiations promptly,” Jon Holden, the head of the IAM District 751 union, said in a statement Wednesday evening.

Boeing employees, including assembler Tyrone Hipolito, centre, work the picket line
Boeing employees, including assembler Tyrone Hipolito, centre, work the picket line (Lindsey Wasson/AP)

“This is workplace democracy — and also clear evidence that there are consequences when a company mistreats its workers year after year.”

A spokesperson for Boeing said officials did not have a comment on the vote.

The labour stand-off comes during an already challenging year for Boeing, which became the focus of multiple investigations after a door panel blew off a 737 Max plane during an Alaska Airlines flight in January.

The strike has deprived the company of much-needed cash that it gets from delivering new planes to airlines.

On Wednesday, the company reported a third-quarter loss of more than six billion dollars (£4.6 billion).

Union 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.

Boeing mechanic Eugenio, who preferred not to give a last name, sounds a bullhorn while holding a sign
Boeing mechanic Eugenio, who preferred not to give a last name, sounds a bullhorn while holding a sign (Lindsey Wasson/AP)

The latest rejected offer included pay raises of 35% over four years. The version that union members rejected when they voted to strike last month featured a 25% increase over four years.

The union, which initially demanded 40% pay boosts over three years, said the annual raises in the revised offer would total 39.8%, when compounded.

Boeing has said that average annual pay for machinists is currently $75,608 (£57,800).

Boeing workers told Associated Press reporters that a sticking point was the company’s refusal to restore a traditional pension plan that was frozen a decade ago.

“The pension should have been the top priority. We all said that was our top priority, along with wage,” Larry Best, a customer-quality coordinator with 38 years at Boeing, said on a picket line outside a Boeing factory in Everett, Washington.

“Now is the prime opportunity in a prime time to get our pension back, and we all need to stay out and dig our heels in.”

The strike began on September 13 and has served as an early test for Boeing chief executive Kelly Ortberg, who started in the role in August.

The last Boeing strike, in 2008, lasted eight weeks and cost the company about 100 million dollars (£77.1 million) daily in deferred revenue.

A 1995 strike lasted 10 weeks.