(NewsNation) — The Federal Aviation Administration administrator testifies before lawmakers Tuesday at a House Transportation Committee hearing focused on safety in the skies.

Lawmakers asked Michael Whitaker about his agency’s investigation into Boeing’s 737 Max 9 planes, especially after new reports from Monday in which the company announced a potential issue with some of its planes’ fuselages.

Tennessee Rep. Steve Cohen, D, said Boeing needs to be held accountable for recent incidents and complacency isn’t something that the aviation industry can afford.

Whitaker testified that the FAA’s number one priority is safety and that the recent Boeing incidents reminded the agency that it can’t be complacent.

Since Whitaker’s swearing-in to FAA administrator last fall, he said he has focused on addressing potential risks to the safety of the national area space, specifically in these three areas: Significant safety events, air traffic controller hiring and continuous safety improvements.

“We will continue to work this issue until we reach our goal of zero significant safety events,” Whitaker said.

In a public letter to its team, Boeing said on Monday that an employee of a supplier reported finding improperly drilled holes in window frames, impacting around 50 planes that had not yet been delivered or in service.

Boeing added that the problem was not reported on any current planes in operation.

The committee also focused on the fallout from the Alaska Airlines incident last month when a door plug blew off a plane during the fight, leaving a gaping hole on the side of the aircraft.

Lawmakers asked questions about possible quality control issues with Boeing production lines from before that incident and if the FAA has found any lapses since it started its own investigation into the company.

“They have had repeated problems with quality and safety. And I want to know why. And I want to know what we’re doing about it in the FAA to make sure that we’re going to keep that quality as much as we can,” Rep. Jeff Van Drew, R- N.J., said.

The official National Transportation Safety Board investigation into the Alaska Airlines incident remains ongoing and a preliminary report could be released later this week.

Since that incident, the FAA says over 90% of its Max 9 planes have been inspected and cleared for service.