Boeing Co. concluded during the development of the 737 Max that if pilots failed to recognize a malfunction on a critical flight-control feature it could prove catastrophic, but the company didn’t notify U.S. regulators, a key lawmaker said Monday.

Representative Peter DeFazio, the Oregon Democrat who is chairman of the Transportation Committee, speaking to reporters before two days of testimony by Boeing Chief Executive Officer Dennis Muilenburg, said that is one issue the executive will be questioned about.

The issue, DeFazio said, revolves around the feature that helped trigger two fatal crashes on the 737 Max that killed 346 people, known as Maneuvering Characteristics Augmentation System. If it activated for 10 seconds and pilots didn’t react, it would prove “catastrophic,” he added. That information should have prompted a more thorough review by the Federal Aviation Administration, he said.

“Now that was never clearly communicated to the FAA, as far as we can tell,” DeFazio told reporters Monday in an interview. “Was that intentional withholding or unintentional?”

Muilenburg is to appear before the Senate Commerce Committee on Tuesday, and DeFazio’s committee on Wednesday.

Senator Roger Wicker, a Mississippi Republican and the committee’s chairman, told reporters on Monday that he forsees a legislative response once the inquiries into the Max have been completed.

”I think there’ll be some statutory fixes,” Wicker said at the Capitol. He added that among the questions he had for Boeing were: “is the plane ready to go, and then what mistakes were made and what’s to prevent them from happening in the future.”

Boeing didn’t immediately respond to a request for comment on DeFazio’s comments. Muilenburg in his written testimony set to be delivered to the Senate panel said the company made mistakes and is learning lessons.

The company has said that the plane was designed and certified following all U.S. regulations.