Preliminary NTSB report on Boeing 737 Max 9 Alaska Airlines flight finds missing bolts led to mid-air door blowout

Four bolts holding the Boeing 737 Max 9 door plug in place were missing last month when part of a plane blew out on an Alaska Airlines flight, the National Transportation Safety Board found in a preliminary report released on Tuesday. 

The door plug, which covers an unused exit door, is typically secured with four bolts to prevent it from moving vertically, according to the report. The door blew off an Alaska Airlines Max 9 at about 16,000 feet over Oregon during a trip to California on Jan. 5th, forcing an emergency landing. 

The incident forced the FAA to order a temporary global grounding of Boeing 737 Max 9 planes and “immediate inspections” the FAA said at the time. 

The agency wrote in the report, “four bolts that prevent upward movement of the MED plug were missing before the MED plug moved upward off the stop pads.”

Kathryn Krupnik contributed reporting

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