More than 33,000 unionized Boeing workers went on strike Friday, rejecting what they say were unfair terms of a deal the embattled aerospace company tentatively reached with their union.

The rejected deal tried and failed to win over workers by offering a 25 percent wage increase and promised to build Boeing’s next jet in the Puget Sound region in Washington, which Boeing claimed offered "job security for generations to come.

But after International Association of Machinists and Aerospace Workers (IAM) District 751 president Jon Holden urged the union to accept the deal—which Boeing said was the “largest-ever general wage increase” in the company’s history—hundreds of Boeing employees immediately began resisting ahead of a Thursday vote that ultimately doomed the deal.

Instead of agreeing to a deal that compromised the desired 40 percent wage increases and eliminated workers’ annual bonuses, about 96 percent of workers voted to strike, The Washington Post reported. Rather than take what Boeing offered, workers seized rare leverage amid Boeing’s financial and production woes to pursue better terms.

Boeing workers have not walked out since 2008, when a 57-day strike cost Boeing about $1.5 billion, the Post reported. Analysts told Bloomberg that the current strike is estimated to last about 50 days, too, potentially costing Boeing between $3 billion and $3.5 billion.