"Airline Safety Concerns: Loose Door Parts Pose Threat to Boeing Jets"

An aviation expert suspects investigators will focus on the Boeing assembly line to determine the cause of a door plug detaching from an Alaska Airlines Boeing 737 Max 9, prompting a midair emergency. United Airlines found loose bolts on its 737 Max 9 fleet, leading to flight cancellations. NTSB recovered the door plug and is investigating previous incidents on the same plane. Boeing CEO canceled a leadership summit and emphasized safety, while the FAA ordered all 737 Max 9 aircraft to remain grounded. Experts urge patience as the NTSB investigation unfolds to determine the cause of the incident.