Boeing’s share price fell sharply on Monday, in the first trading session after part of the fuselage of one of its 737 Max 9 jets blew out on an Alaska Airlines flight on Friday night.

Boeing’s stock slipped nearly 7 percent and Spirit AeroSystems, which made the door plug that was torn from the plane, fell about 8 percent, recovering from a far steeper decline in early trading.

The Alaska Airlines flight departing from Portland, Ore., lost the mid-cabin door plug midair, exposing passengers to howling winds and forcing an emergency landing. None of the 171 passengers and six crew members aboard were seriously injured.

The Federal Aviation Administration on Saturday ordered U.S. airlines to ground all their Boeing 737 Max 9 planes. The National Transportation Safety Board is investigating the incident.