Multiple system failures led to Alaska 737-9 door plug blowout, NTSB concludes

An investigation by the National Transportation Safety Board (NTSB) into the door plug blowout aboard an Alaska Airlines Boeing 737 MAX 9 has concluded that “multiple system failures” led to the incident on January 5, 2024.  

On June 24, 2025, at an NTSB board meeting, the agency chair Jennifer Homendy laid bare the “long chain of events” that caused the door plug seperation and the single reason why the “catastrophe” was averted.  

“Let me be clear: An accident like this does not happen because of an individual, or even a group of individuals. Aviation is much more resilient than that. An accident like this only happens when there are multiple system failures,” said Homendy in her opening remarks. 

Homendy praised the actions of the Alaska Airlines pilots and cabin crew for their life-saving efforts during the emergency.  

“When every second counts, as it did on Flight 1282, training to the point of muscle memory is paramount,” she said. “In this case, the crew knew precisely what to do — they acted without hesitation. It saved lives. And yet, the crew shouldn’t have had to be heroes.  Because this accident never should have happened.”  

NTSBCiting previously unreported details, Homendy explained that during the emergency there were three lap children and four unaccompanied minors — one of whom was just six years old and on his first ever flight.  

The captain, the first officer, three flight attendants and 164 passengers had just departed Portland International Airport and were climbing at around 15,000 feet when the left mid-exit door plug separated from the aircraft, causing a rapid depressurization. 

“I cannot overstate the seriousness of this event, which jeopardized the lives of all 177 souls onboard, and perhaps countless others on the ground.” Homendy told the NTSB and gathered media representatives.  

To accompany the meeting, the NTSB published an executive summary of the final investigation report that will be released in the coming weeks. 

As with Homendy’s opening statement, the strongest criticism was laid at the door of Boeing and the Federal Aviation Administration (FAA). 

NTSBThe executive summary said Boeing failed to “provide adequate training, guidance and oversight” to its factory workers and that the FAA was ineffective in ensuring the manufacturer addressed “repetitive and systemic” nonconformance issues associated with its parts removal process.   

“The safety deficiencies that led to this accident should have been evident to Boeing and to the FAA and were therefore preventable,” Homendy said. 

It has been known for some time that the door plug separated from the aircraft because four bolts that would secure the panel from moving upward vertically had not been in place. 

When the jet was being built, Boeing personnel opened the door plug to allow access so that rivet rework could be performed. However, when the door plug was returned, the bolts were not reinstalled.  

“While Boeing’s procedures called for specific technicians to open or close MED plugs, none of the specialized workers were working at the time the door plug was closed. The absence of proper documentation of the door plug work meant no quality assurance inspection of the plug closure occurred,” the NTSB noted.  

NTSBThe NTSB also concluded that in the two years before the accident, Boeing’s voluntary safety management system (SMS) was inadequate, lacked formal FAA oversight, and did not proactively identify and mitigate risks.  

The investigation found that accurate and ongoing data about overall safety culture is necessary for an SMS to be successfully integrated into a quality management system. 

“This time, it was missing bolts securing the door plug. But the same safety deficiencies that led to this accident could just as easily have led to other manufacturing quality escapes and, perhaps, other accidents,” Homendy said during her opening statement.  

Probable cause – summary

In its summary of the Alaska Airlines incident the NTSB said:

We determined that the probable cause of this accident was the in-flight separation of the left mid exit door plug due to Boeing’s failure to provide adequate training, guidance, and oversight necessary to ensure that manufacturing personnel could consistently and correctly comply with its parts removal process, which was intended to document and ensure that the securing bolts and hardware that were removed to facilitate rework during the manufacturing process were properly reinstalled.  

Contributing to the accident was the FAA’s ineffective compliance enforcement surveillance and audit planning activities, which failed to adequately identify and ensure that Boeing addressed the repetitive and systemic nonconformance issues associated with its parts removal process. 

Boeing’s redesigned mid cabin door plug 

In reference to Boeing’s redesigned mid-cabin door plug, the NTSB said that the company should continue the certification process for the enhancement and, once certified, fit it to all new planes.  

“We also recommended that Boeing issue a service bulletin to address retrofitting in-service airplanes, and that the FAA issue an airworthiness directive to require that all in-service MED plug-equipped airplanes be retrofitted with the design enhancement,” the NTSB said.  

Statements from key stakeholders 

Boeing  

We at Boeing regret this accident and continue to work on strengthening safety and quality across our operations. We will review the final report and recommendations as we continue to implement improvements. 

The FAA 

The FAA takes NTSB recommendations seriously and will carefully evaluate those issued today. The FAA has fundamentally changed how it oversees Boeing since the Alaska Airlines door-plug accident and we will continue this aggressive oversight to ensure Boeing fixes its systemic production-quality issues. We are actively monitoring Boeing’s performance and meet weekly with the company to review its progress and any challenges it’s facing in implementing necessary changes. We have a full complement of safety inspectors in Boeing’s facilities, and they are conducting more targeted audits and inspections. While Boeing is making progress, we will not lift the 737 monthly production cap until we are confident the company can maintain safety and quality while making more aircraft.   

Sean Duffy – US Department of Transportation Secretary 

The last administration and Boeing took their eye off the ball. They were distracted and safety was put at risk. That can never happen again. Under this new administration, safety is paramount and it drives everything we do. Whether it’s building an all-new air traffic control system or ensuring Boeing and other manufacturers are delivering safe products, we will not hesitate to implement changes.   The FAA has fundamentally changed how it oversees Boeing. We have strengthened our oversight to address systemic production-quality issues and ensure accountability. A number of the NTSB’s recommendations have already been implemented, and those that have not are currently under review. 

We are closely monitoring Boeing’s performance, meeting weekly with company leadership to review progress and challenges in implementing necessary reforms. FAA safety inspectors are embedded in Boeing’s facilities, conducting targeted audits and inspections. 

You can read the full executive summary and the NTSB’s safety recommendations on its website 

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