Investigation Summary
The accident aircraft was delivered to Alaska Airlines in October 2023. During final assembly at Boeing, the left mid exit door (MED) plug was opened to allow for the replacement of damaged rivets on the surrounding fuselage frame. This work was performed by Spirit AeroSystems personnel at the Boeing facility. However, the removal of the door plug was not documented in Boeing's formal 'removal record' system. Consequently, when the rivet work was completed and the plug was closed, the four vertical movement arrestor bolts required to secure the plug were not reinstalled. Without these bolts, the plug was held in place only by friction and stop fittings. Over 154 flight cycles, the plug gradually shifted upward until the stop fittings disengaged, leading to the explosive decompression on January 5, 2024.
Final Conclusions
The NTSB determined the probable cause was Boeing's failure to ensure manufacturing personnel complied with parts removal processes, leading to the missing bolts. Contributing factors included the FAA's ineffective oversight of Boeing's manufacturing quality and systemic nonconformance issues.
Video Analysis
Boeing 737 Exit Door Plug Blowout NTSB Board Meeting • Alaska Airlines Flight 1282 — Official NTSB board meeting and animation detailing the in-flight separation of the left mid-exit door plug and the subsequent investigation into Boeing's manufacturing processes.
Watch on YouTube ↗If playback is blocked, the owner has disabled embedding — use the link above.
Systems & Failure Modes
Mid Exit Door (MED) Plug
A non-operational door structure used to plug an exit opening when the airline's seating configuration does not require an active emergency exit.
Arrestor Bolts
Four bolts (two on the upper guide fittings and two on the lower hinge brackets) designed to prevent the door plug from sliding upward and disengaging from its stop pads.
Stop Fittings
Twelve pads (six on each side) that transfer the internal pressure loads from the door plug to the airplane's fuselage frame.
Interesting Facts
- 01The door plug was recovered from a backyard in the Cedar Hills neighborhood of Portland.
- 02The Cockpit Voice Recorder (CVR) was overwritten because the circuit breaker was not pulled after landing, losing the 2-hour audio loop.
- 03The aircraft had only 510 total flight hours and 154 cycles at the time of the accident.
- 04Four vertical movement arrestor bolts were missing from the recovered door plug and showed no evidence of being present at the time of failure.
- 05The rapid decompression caused the headrests of seats 25A and 26A to be sucked out of the aircraft.
Safety Actions & Advisories
FAA Emergency Airworthiness Directive
The FAA grounded approximately 171 Boeing 737-9 MAX aircraft for immediate inspections of door plugs following the accident.
Boeing Design Enhancement
Boeing was directed to develop a design enhancement to ensure MED plugs cannot be closed if securing hardware is missing.
CVR Recording Duration Increase
The NTSB reiterated the need for 25-hour Cockpit Voice Recorders to prevent data loss, as occurred in this investigation.