The risk of a strike at Boeing appears to be growing, as factory workers complain about a contract offer that their union negotiated with the giant aircraft manufacturer.

The president of the union local that represents 33,000 Boeing workers predicted that they will vote against a deal that includes 25% raises over four years and a promise that the company’s next new airplane will be built by union members in Washington state.

“The response from people is, it’s not good enough,” Jon Holden, the president of the union local, told The Seattle Times newspaper.

Members of the International Association of Machinists and Aerospace Workers in the Seattle area and machinists at other locations in Washington and California are scheduled to vote Thursday on the Boeing offer and, if they reject it, whether to go on strike beginning Friday.

Union members have gone on social media to complain about the deal. Hundreds protested during a lunch break at their plant in Everett, Washington, chanting, “Strike! Strike! Strike!” according to the Seattle Times.

Holden, who joined the union bargaining committee in unanimously endorsing the contract, told the newspaper he doesn’t believe he can secure the votes to ratify the proposed contract.

Boeing did not immediately respond when asked for comment.

Unlike strikes at airlines, which are very rare, a walkout at Boeing would not have an immediate effect on consumers. It would not result in any canceled flights. It would, however, shut down production and leave Boeing with no jets to deliver to the airlines that ordered them.

On Sunday, the company and the union local, IAM District 751, announced they had reached a tentative agreement that featured the 25% wage hike and would avoid a suspension of work on building planes, including the 737 Max and the larger 777 widebody jet.

The deal fell short of the union’s initial demand for pay raises of 40% over three years and restoration of traditional pensions that were eliminated in union concessions a decade ago. Workers would get $3,000 lump-sum payments, increased contributions to retirement accounts and the commitment about working on the next Boeing airplane.

Holden said in a message to members Monday, “We have achieved everything we could in bargaining, short of a strike. We recommended acceptance because we can’t guarantee we can achieve more in a strike.”

A strike would add to setbacks at Boeing. The company, headquartered in Arlington, Virginia, has lost $27 billion since the start of 2019 and is trying to fix huge problems in both aircraft manufacturing and its defense and space business. A new CEO has been on the job a little over a month.

Boeing shares were down 3% in afternoon trading.