Boeing's largest white-collar union delivered a stinging rebuke to management on Friday, with engineers and technical employees voting overwhelmingly to reject a tentative four-year contract and authorize a strike when their current agreement expires in October. The Society of Professional Engineering Employees in Aerospace, known as SPEEA, represents roughly 17,000 engineers, scientists, analysts and technicians whose work underpins Boeing's design, testing and certification programs, including the long-delayed 737 MAX 10 and 777X.

Members of the professional unit voted 64.3 percent against the deal, while the technical unit rejected it 71.9 percent, on turnout of 92 percent of eligible voters, according to a breakdown released by the union. Strike authorization passed even more lopsidedly, with 87.8 percent of engineers and 89.7 percent of technicians giving negotiators the green light to call a walkout.

Why members said no

At issue was how Boeing structured pay. The rejected offer touted a headline wage increase of 29.4 percent over four years, the largest SPEEA members have been offered since 1983, plus three additional paid leave days and new provisions governing how artificial intelligence tools are used in engineering work. But members balked at a clause capping annual inflation-adjusted raises at 3 percent, even as Seattle-area consumer prices climbed 4.5 percent over the past year, a gap the union said would leave real pay falling behind the cost of living year after year.

No strike can happen before the current contract expires on October 6, and none is scheduled yet. SPEEA said its negotiating team will now survey members on what changes would win approval and try to get back to the bargaining table with Boeing before that deadline, according to CNBC's report on the vote. The union struck for 40 days in 2000, its last major work stoppage, but approved contract extensions without a strike in 2016 and 2020.

"Our negotiation team is prepared and willing to work with the company toward meaningful movement so that we can come to agreement on new contracts before Oct. 6," SPEEA said in its statement announcing the results.

A SPEEA walkout would land at a delicate moment for Boeing, which is still working through the fallout of the seven-week machinists' strike in 2024 and is racing to finish certification testing on the 737 MAX 10 and 777X programs, both already years behind schedule. Because SPEEA members handle design, testing and regulatory paperwork rather than final assembly, a stoppage could stall certification even if the production line kept running, a different kind of disruption than the machinists strike caused.

For now, both sides say they intend to keep talking. Members cited persistent distrust of management as a driver of the "no" vote even though the union's own negotiating team had unanimously recommended the rejected deal, a split that suggests Boeing has more convincing to do on the shop floor than it did at the bargaining table.