United, Alaska Find Loose Parts on Some Boeing 737 MAX 9 Jets

United Airlines and Alaska Airlines have discovered loose parts on Boeing 737 MAX 9 jets that they have inspected after a near-catastrophe on a flight Friday, signaling Boeing’s issues go beyond the aircraft that made an emergency landing.

Separately, investigators at the National Transportation Safety Board, in a briefing late Monday, said an emergency exit-sized door plug blew out of the Alaska Airlines plane at around 16,000 feet after moving off a set of stops that are designed to keep it attached to the plane.