Members of Boeing Co’s engineers union voted down a proposed contract and authorized strikes, setting the stage for a challenging few weeks for the US planemaker just as it’s in the final stages of certification for crucial aircraft models.

The SPEEA union said in a statement that a majority of its professional and technical unit members voted against the contract terms and in favor of a strike authorization.  

The union said that it would survey members on what they would need from Boeing in order to accept the proposal.

Boeing is in the final stages of certifying its long-delayed 737 Max 10 and 77X models, and a strike by its engineers and technicians could impact that process.

The SPEEA represents engineers, scientists, pilots, technicians, analysts and other professionals working in five states. It does not represent Boeing’s production workers.

“We gave a strong contract offer to position our employees among the market leaders in pay and benefits in the Pacific Northwest,” Boeing Vice President Ben Nimmergut said in an emailed statement, adding that the earliest a strike could occur is Oct 7.

Boeing has no further talks scheduled with the union, he said.