Bolts were missing from Boeing jet that suffered blowout: NTSB

A preliminary report by the National Transportation Safety Board states that there were bolts missing from a door plug that blew off of the side of a Boeing 737 Max 9 plane during a Jan.5 Alaska Airlines Flight.

The plane had been flying over Oregon at the time. Only minor injuries were reported.

Following this incident, the FAA grounded all Max 9s in the United States for nearly three weeks, forcing Alaska and United Airlines to cancel more than 1,000 flights between them.

Released Tuesday, the NTSB report does not determine the cause of the blowout, but it can reveal key facts about what happened.

In the report, it says that when the plane was at 16,000 feet, the captain heard a loud bang. His headset was pushed up, nearly falling off his head, the report said, while the flight crew immediately donned oxygen masks.