A Boeing 737-800 aircraft belonging to the American company United Airlines was missing an exterior panel when it landed after a flight between San Francisco and Medford on Friday evening, Swedish time.

The plane landed safely and the discovery was made during a post-flight inspection, Medford Airport officials told the AP. No debris was found on the airport's airfield.

The missing panel was located on the underside near where the landing gear is deployed, according to the airline.

The incident is one of several serious safety incidents that have affected planes from aircraft manufacturer Boeing in recent times.

Federal prosecutors have opened a criminal investigation into an incident in January when a door plug on an Alaska Airlines plane came loose, leaving a large hole in the aircraft thousands of feet above sea level. 

Things were sucked out of the hole and the plane was forced to make an emergency landing in Portland. No one was hurt, the door stopper was later found in a private garden.

Source: TT-DI.SE