Faulty door panel on Alaska Airlines flight had no bolts installed, NTSB says in preliminary report

The door panel on an Alaska Airlines Boeing 737 that fell off midair had no bolts installed on the door plug, according to preliminary findings released Tuesday by the National Transportation Safety Board.

A picture of the plane in a factory in Renton, Washington, revealed the lack of bolts, the NTSB said. “Photo documentation obtained from Boeing shows evidence of the left-hand MED plug closed with no retention hardware (bolts) in the three visible locations," the report said, using an acronym for the middle exit door.

However, it was not clear at what stage in the manufacturing process the plane was in when the photo was taken - NBC News