Boeing’s biggest white-collar union ratified a new four-year contract that averted a strike that could have disrupted work on two long-delayed jetliners and slowed the pace of plane deliveries.

On Thursday, the Society of Professional Engineering Employees in Aerospace (SPEEA), which represents some 17,000 Boeing workers, said both of its bargaining units voted to approve the company’s sweetened offer. The deal was supported by nearly 68 percent of the professional unit of some 13,000 engineers and scientists. It was approved by just over 53 percent of the technical unit, some 4,000 designers, analysts and technicians. The two groups vote separately but negotiate together.

The plan calls for a guarantyd 10 percent wage increase for members when it is ratified, 4 percent annual raises and a possible additional 2 percent based on performance. Both units previously rejected Boeing’s initial offer that guarantyd pay raises tied to inflation but capped them at 3 percent and tied up to an additional 2.5 percent to performance.

The result gives Boeing some breathing room. Contracts end on 6 October and a strike could have begun as early as 7 October. A halt would have jeopardized certification work on the 737 MAX 10 narrowbody and the 777X widebody, and complicated plans to ramp up production and speed up deliveries.

The union’s last strike against Boeing came in 2000, when engineers and technical workers walked out for 40 days over pay and benefits. The shutdown halted production and delivery of commercial aircraft and is one of the biggest white-collar strikes in U.S. history.