(The Center Square) – Boeing machinists are on strike.

Aircraft assembly workers at Boeing factories in Washington, Oregon and California overwhelmingly rejected a tentative contract that would have increased wages by 25% over four years.

The previous contract between the company and the International Association of Machinists and Aerospace Workers union, or IAM 751, expired at midnight.

According to a post from IAM District 751 President Jon Holden, 94% voted to reject the contract and 96% voted to strike.

Union rules required a vote of more than two-thirds to authorize a walkout.

The tentative contract that was rejected was reached between the company and union bargaining team members last weekend, and though Holden urged members to accept the deal, he conceded it was up to members to vote it up or down.

By the end of the four-year contract, the average machinists would have earned $106,350, according to Boeing. The rejected proposal would have also lowered health care costs, and a larger increase in what Boeing contributes to workers’ retirement plans. The company was also offering a guarantee that the next new aircraft would be built in Washington, but only if the offer which was just rejected, had been accepted.

The strike involves 33,000 machinists, most of them in Washington, but also Oregon and California, presents another setback for a company having a rough go over the last few years.

There were fatal crashes of Boeing’s 737 MAX planes in 2018 and 2019, in Ethiopia and Indonesia, with both blamed on faulty parts that affected flight controls.

MAX planes were grounded for more than a year and a federal investigation resulted in Boeing officials pleading guilty to fraud charges earlier this year. The agreement, and an earlier federal fine brings total fines against the company to $487.2 million, which the Justice Department says is the legal maximum for the fraud charge.

The deal also requires the company to invest more than $450 million on safety improvements and Boeing will be on court-supervised federal probation for three years.

On Jan. 5 , the door panel on a Boeing 737 MAX 9 aircraft blew off at 16,000 feet, which caused the cabin to depressurize before the crew and passengers landed safely back at Portland International Airport. The panel was later found to have four missing bolts.

Most recently, Boeing’s Starliner returned to Earth without its two-person crew.

NASA astronauts Butch Wilmore and Suni Williams launched aboard Boeing’s Starliner spacecraft on June 5 for its first crewed flight. They expected to be home in time for the Fourth of July, but issues with the spacecraft forced Boeing to bring it back to Earth without the crew. Wilmore and Williams are now at the International Space Station, and according to USA today, may not return to earth until January, with that responsibility now taken up by Boeing’s competitor, SpaceX.

U.S. Congressman Adam Smith, D-Wash., released a statement Thursday evening regarding the strike, which said, in part: “I strongly urge the parties to return to the negotiating table and participate in good-faith discussions that result in a strong agreement … Unions remain essential for workers and their families, and I will always champion the right to organize and collectively bargain for better working conditions. I sincerely hope that the parties reach an agreement that respects all employees as well as the company as a whole.”

Boeing stock was down more than $6 per share by midday Friday, at $156. At the end of 2023, Boeing stock was valued at $260 per share.