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 identifying and addressing aviation safety risks in the wake of a mid-air blowout on a Boeing Co. jet, the agency’s top official plans to tell lawmakers 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.