Upon inspection, the aircraft was held for repair, then flown back to the United States for additional investigation and repair. The plane is now back in service, Black said.
"An event such as that event is incredibly rare," Black said. "Everything about the event is under investigation."
He said pilots and line maintenance do a walk-around inspection of the aircraft before flights, "so had they noticed anything unusual about the aircraft they would have flagged that." However, the incident occurred toward the end of the flight, and it's unclear what may have caused the door to fall off.