United Airlines has reported multiple issues with door plugs on its Boeing 737 MAX 9 aircraft, similar to the part blown out during an Alaska Airlines flight earlier this week, during inspections mandated by the US’ Federal Aviation Administration (FAA). 

The airline, which has the largest fleet of MAX 9 aircraft in the US, said it had “found instances that appear to relate to installation issues” with the door plugs, including bolts that needed additional tightening, during the inspections ordered under the FAA’s Emergency Airworthiness Directive (EAD). 

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Alaska had also reported reports of “loose hardware” during its own initial investigations of its MAX 9 fleet, before the FAA had published its guidance on formal inspections. 

United and Alaska’s discoveries are likely to heighten the scrutiny around Boeing, and door plug manufacturer Spirit AeroSystems, which began after a fuselage panel came off an Alaska plane soon after takeoff, causing parts of the aircraft interior to be ripped out of the passenger plane. 

The isolated incident, which caused no injuries or fatalities, has had a significant impact on the aviation industry as airlines using the MAX 9 aircraft have taken their own steps to ensure their fleets’ safety. That followed Boeing’s multi-operator message and the FAA’s grounding of around 171 planes with its EAD, covering those which were configured in the same way as the affected aircraft. 

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United said it had cancelled at least 200 flights that were meant to be flown by a MAX 9 while it conducts the necessary inspections, and expected significant disruption to continue. 30 flights were transferred to other aircraft.

According to news outlet The Air Current, which was the first to report on United’s findings, the issues have been found on at least five of the airline’s 79 MAX 9s.

On the FAA’s part, it approved a method to allow airlines to comply with the EAD which involved inspecting both left and right cabin door exit plugs, door components, and fasteners and correcting any issues. 

While Alaska and United’s shares don’t appear to have been much affected by the discoveries, Boeing’s have continued to fall, dropping more than 1% by midday on Tuesday 9 January.

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