The National Transportation Safety Board (NTSB) has concluded that four bolts, which were meant to secure a door plug on an Alaska Airlines Boeing 737 MAX 9, were indeed missing. The agency issued its preliminary findings regarding the door blowout incident that occurred on January 5th.

During the flight, designated as AS1282 from Portland, Oregon, to Ontario, California, the left mid-exit door (MED) plug tore off shortly after takeoff, resulting in a significant breach in the fuselage and cabin decompression. Following a detailed inquiry, the NTSB verified that the fuselage had been supplied to Boeing with flaws near the door plug.

The unplanned detachment of the MED plug originated from a component manufactured by Spirit AeroSystems in Malaysia on March 24, 2023, and subsequently transported to the company’s headquarters in Wichita, Kansas, on May 10th. According to the NTSB, it was then “installed and configured on the fuselage” of the MAX 9. As part of its investigation, the agency, accompanied by a Human Performance Investigator, visited Spirit AeroSystems to scrutinize critical documentation related to the fabrication of the unplanned plug and to witness the installation of a MED plug.

The agency noted a discrepancy during the fabrication process of N704AL’s plug, indicating that it was not completely flush with the fuselage by 0.01 inches. Nonetheless, Spirit AeroSystems deemed it “functionally acceptable” prior to its delivery to Boeing on August 20th.

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