New York, New York - Despite efforts to avoid a labor strike this fall, Boeing's CEO warned Wednesday that a stoppage would halt key plane certification efforts and dent production.

"We're working very hard to try to avoid that kind of a work stoppage," Boeing Chief Executive Kelly Ortberg said of negotiations with the Society of Professional Engineering Employees in Aerospace, or SPEEA.

"The impact would be significant if we did have a strike," Ortberg said. "Essentially, 777X certification program shuts down until we get the engineers back, and it will have ripple effect even into our production."

Ortberg's comments come after negotiators from SPEEA, a white-collar labor union composed of engineers and other professional employees, prepare to sell the latest proposed offer to its membership.

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SPEEA negotiators announced an improved offer on September 11 after members the previous month roundly rejected an earlier proposal, creating the conditions for a potential strike when the current contract expires on October 6.

"The latest proposal isn't everything we'd asked for, but it represents a real step forward toward improving our pay and work lives and rebuilding the relationship between Boeing leadership and our union's members," SPEEA negotiators said of provisions that included a 10% wage increase, among other boosts.

Ortberg contended with a more than seven-week strike of Boeing machinists in the fall of 2024 shortly after joining the company earlier that year.

Addressing a Morgan Stanley conference, Ortberg said Wednesday he was "very hopeful" about averting another strike.

He expects a union vote on the contract in the "next couple of weeks."

On other matters, Ortberg said he anticipates US certification of the 737 MAX 10 "very soon" after winning certification from the Federal Aviation Administration (FAA) for the 737 MAX 7 in early August.

Flight testing is done for the 737 MAX 10, leaving final documentation demands from the agency. The certifications are a key element of Boeing's plan to boost plane production in the coming years and improve financial performance after a lengthy downturn due to safety problems.

The aviation giant is still conducting flight testing on the 777X and awaiting key authorizations for engine testing.

"We may see some of the testing spill into the next year," Ortberg said of the 777X. "We're still planning on 2027 deliveries."