Bolts on Alaska 737 Max 9 Door Plug Appeared to Be Missing, Investigators Say

Four bolts appeared to be missing on a door plug that blew off from a Boeing 737 Max 9 operated by Alaska Airlines, according to a preliminary report from the National Transportation Safety Board. 

On January 5, a door plug suddenly fell off an Alaska plane just minutes after takeoff, leading to a rapid decompression on the aircraft. The incident had prompted the Federal Aviation Administration to ground the Max 9 for nearly a month.

Here is what the NTSB said:

• The NTSB report said the nature of the damage and “absence of deformation” around the holes in question “indicate that the four bolts that prevent upward movement… were missing.” 
• The document came to no conclusions as to how the bolts meant to keep the door plug intact went missing. The agency said it plans to interview Boeing and Spirit Aerosystems — the aircraft supplier that manufactured the fuselage and door plug — at a future date. 
• The NTSB report said the door plug Spirit delivered to Boeing on August 31, 2023 had come with certain defects. Those defects required Boeing to open and remove the bolts of the door plug.
• “The investigation continues to determine what manufacturing documents were used to  authorize the opening and closing of the left MED plug during the rivet rework,” the report read. Outlets like The New York Times and The Seattle Times had previously reported that Boeing may have incorrectly installed the door plug after receiving it from Spirit. 

Boeing and Spirit Face the Music

Spirit said in a statement on Tuesday that it plans to work closely with Boeing to improve its production processes.

“As we review the NTSB’s preliminary report, we remain focused on working closely with Boeing and our regulators on continuous improvement in our processes and meeting the highest standards of safety, quality and reliability,” Spirit said.  

Due to the grounding, the FAA decided to halt the production expansion of the 737 Max. Boeing said in its last earnings call that it is manufacturing 38 737 Maxes a month until regulators are satisfied with its production and quality control. 

Boeing CEO Dave Calhoun said Boeing is taking full accountability for the incident.

“Whatever final conclusions are reached, Boeing is accountable for what happened,” Calhoun said in a statement. “An event like this must not happen on an airplane that leaves our factory. We simply must do better for our customers and their passengers.”