Missing bolts may be the reason a door blasted away from a Boeing 737 Max shortly after take-off last month, according to a new report.
The US National Transportation Safety Board’s (NTSB) initial findings from an inquiry into the incident suggest four key bolts had not been properly fitted.
The bolts were meant to fasten the unused door to the fuselage, but appeared to be missing from the body of the craft, the investigation has found.
The panel was covering an unused emergency exit, known as a door plug, and fell away minutes after Alaska Airlines Flight 1282 took off.
The door plug was fixed by four bolts, secured at 12 different locations along the side of the plug and door frame.
The NTSB said in January that all 12 stop fittings had become unsecure during the flight.
The door plug was manufactured by Spirit AeroSystems, Boeing’s supplier. They had originally installed the fuselage before delivering the craft to Boeing.
According to the report, the door plug was removed in the factory due to a fault that had occurred during the production process.
Just last month, United Airlines said it had found loose bolts on multiple 737 Max 9 aircraft, compounding issues related to the installation of several panels on the planes.
The ill-fated flight, which was bound for Ontario, California, was forced to return to Portland, Oregon, after a section of the cabin wall was ripped off, leaving a hole one passenger reportedly described as being “as wide as a refrigerator”.
Footage on social media showed the hole after the cabin wall and window had blown out, with oxygen masks released and dangling from the cabin ceiling. The seat next to the window was unoccupied.
The plane landed safely back in Portland with all 177 passengers and crew, with the airline reporting that several passengers suffered injuries that were non-serious but required medical attention.
Although all passengers and crew members were returned safely to the ground, mobile phones and a child’s shirt were reportedly sucked out of the gap in the plane.
As a precaution, the Federal Aviation Authority (FAA) grounded all 171 of Max 9 jets, while placing a ban on raising production volumes within the entire fleet.
Thousands of flights were cancelled by providers including Alaska Airlines, Copa Airlines, Turkish Airlines and United Airlines, who were among users of the Boeing 737 Max 9, as a result of the temporary grounding order, which was lifted on 24 January.
The FAA said 94 per cent of the jets have returned to service.
In 2018, the 737 Max was grounded for 20 months worldwide after two fatal crashes linked to poorly designed cockpit software killed 346 people in Ethiopia and Indonesia.
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