A key lawmaker said Wednesday that he opposes giving Boeing Co. more time to certify its Max 10, signaling potential and costly delays for the planemaker’s next model of the 737.

Representative Peter DeFazio, the Oregon Democrat who leads the House Transportation and Infrastructure Committee, said in an opening statement at a hearing that he would oppose Congress extending a waiver it granted to the Max 10.

“The aircraft certification bill gave the FAA a two-year grace period to certify aircraft without the advanced flight crew alerting system, but that grace period should not be extended,” DeFazio said in prepared remarks.

The implications are enormous for Boeing if it has to redesign the Max 10’s flight-control system to add a more modern emergency alerting system. It would make the plane different from other existing Max models, possibly requiring different pilot training for the Max 10. And such changes can take years of additional work and millions of dollars in costs.

Boeing declined 2.15% to $178.72 at the close of the session in New York. Boeing shares have fallen 11.2% so far this year.

The FAA in March wrote to Boeing saying it was concerned the company wouldn’t complete work on the Max 10 before the Congress-imposed deadline of the end of this year. The Max 10 is an extended version of the company’s flagship single-aisle model.

Senator Maria Cantwell, the Washington Democrat who is chairwoman of the Commerce, Science and Transportation committee, has appeared open to giving Boeing an extension.

Asked about DeFazio’s comments, Cantwell spokeswoman Tricia Enright referred to what the senator told the Seattle Times last month. Cantwell said then that if the FAA agreed to an extension, she would as well.

“If the FAA says yes, we need another six months, give them six months,” Cantwell said. “If everybody was in agreement, I would change the date.”

Both Cantwell and DeFazio played a significant role in crafting the original legislation that included the waiver for the Max 10.