On January 5, 2024, a Boeing 737-9 Max airplane operated by Alaska Airlines experienced an in-flight separation of a door plug shortly after departure from Portland International Airport, Oregon, for a scheduled flight to Ontario, California. The airplane made an emergency landing in Portland and all 177 occupants, including 171 passengers, survived. Alaska Airlines immediately grounded all 65 of its 737-9 Max airplanes, and the National Transportation Safety Board (NTSB) launched an investigation of the accident.
On January 6, the Federal Aviation Administration (FAA) issued an emergency airworthiness directive requiring inspections of all 737-9 Max aircraft with mid-cabin door plugs. A door plug is a device used to seal off a fuselage opening when an additional emergency exit door is not required by regulation based on the particular airplane’s seating configuration. The door plugs on the 737-9 Max are held in place by stop fittings pressed against stop pads and secured by upper and lower bolts. Reportedly, both Alaska Airlines and United Airlines, the two U.S. operators of 737-9 Max airplanes, identified loose door plug hardware, including bolts that require additional tightening, during these mandated inspections.
Boeing has been working on revising its instructions to remedy loose door plug hardware, which has extended the grounding until FAA is satisfied that the airplanes can safely return to operation. FAA elaborated that “[t]he safety of the flying public, not speed, will determine the timeline for returning the Boeing 737-9 Max to service.” FAA has also launched an investigation to determine whether Boeing failed to meet regulatory requirements for airworthiness certification due to lapses in product inspections and testing.
The mishap and subsequent grounding came on the heels of Boeing announcing unrelated concerns about potentially loose hardware in the rudder control systems of all 737 Max airplanes in late December 2023. Boeing issued a notice to operators urging inspections of about 1,400 737 Max aircraft in service after an international operator reportedly discovered a missing nut during routine maintenance, and Boeing subsequently found a loose nut on an undelivered airplane.
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