The National Transportation Safety Board (NTSB) has released its preliminary report on the incident involving an Alaska Airlines Boeing 737 MAX 9 that occurred on January 5th. The report reveals significant findings about the incident, which left a gaping hole in the fuselage and caused aircraft decompression.
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Missing Bolts and Fuselage Defects
The NTSB discovered that four bolts meant to secure a door plug were missing from the aircraft. These bolts are key components that ensure the structural integrity of the door plug. Their absence could have contributed to the door plug blowing off in midair. In addition to the missing bolts, the fuselage was found to have defects near the door plug. These defects were present when the fuselage was delivered to Boeing. Despite these issues, the plug, manufactured by Spirit AeroSystems, was still deemed structurally acceptable.
Investigation Details
The aircraft, identified as N704AL, was operating as AS1282 from Portland, Oregon, to Ontario, California, when the left mid-exit door (MED) plug tore off shortly after departure. The NTSB, along with a Human Performance Investigator, visited Spirit AeroSystems to review critical documents regarding the build of the accidental plug and observe the installation of a MED plug. A defect was noted during the build process of N704AL’s plug, indicating that it was not fully flush to the fuselage by 0.01 inches. However, Spirit AeroSystems still determined that it was still “functionally acceptable” before it was delivered to Boeing on August 20th.
Ongoing Investigation
The NTSB's investigation into this incident is ongoing. All aspects of this incident remain under investigation. As more information becomes available, the NTSB will continue to update its findings. This incident underscores the importance of rigorous safety checks and quality control in aircraft manufacturing. It serves as a reminder of the critical role that each component plays in ensuring the safe operation of an aircraft. As the investigation continues, the aviation industry will be watching closely for any further developments and lessons that can be learned from this incident.