Boeing still has to make “significant changes” to improve the quality and safety of its airplanes, according to the head of the Federal Aviation Administration.

The US Federal Aviation Administration is working to overhaul its internal processes for managing safety risks, the head of the agency plans to tell lawmakers at a hearing on Tuesday.

After two crashes of Boeing 737 Max airplanes and a door plug that fell off of another, mid-flight, FAA Administrator Michael Whitaker testified before the House of Representatives about his agency’s oversight of Boeing.

Federal Aviation Administration officials and the House Transportation Committee debated how Boeing could improve safety.

Boeing must do more to improve the aircraft safety following a door plug blowout in January and other mishaps, Federal Aviation Administration Administrator Mike Whitaker told a House committee Tuesday.

The head of the Federal Aviation Administration will tell Congress on Tuesday the agency will hold Boeing accountable to ensure the planemaker is building safe airplanes and will revamp its own safety management program.

The Federal Aviation Administration is working to revamp its oversight process after a door plug detached mid-flight on a Boeing 737 Max jet earlier this year, the head of the US agency said on Tuesday.