US politicians and the flying public are desperate for answers to what caused the panel to rip off a brand-new Alaska Airlines-operated jet, in what has turned into a full-blown safety and reputational crisis for Boeing.
"Whatever final conclusions are reached, Boeing is accountable for what happened. An event like this must not happen on an airplane that leaves our factory," said Boeing President and CEO Dave Calhoun.
The US Federal Aviation Administration grounded 171 of the Boeing 737 MAX 9 planes after the incident, most operated by US carriers United Airlines and Alaska Airlines , for inspections. Those planes were cleared to return to service in late January.
The US National Transportation Safety Board report released on Tuesday focused on how the panel - fitted into this MAX 9 model in place of an optional exit - could have detached from the plane. The plug is held down by four bolts and then secured by "stop fittings" at 12 different locations along the side of the plug and the door frame.
The plug was manufactured by Spirit AeroSystems, the a former subsidiary of Boeing. The part was produced at its facilities in Malaysia.
The report shows the panel had to be removed at Boeing's Renton, Washington, factory before being reinstalled. The initial findings released on Tuesday include photo evidence that the bolts required to hold the plug in place appeared to be missing.
The report found the panel was first removed to repair rivet damage logged by Boeing workers on September 1, 2023, a day after the panel arrived in Renton. Investigators are still trying to determine what documentation was used to authorise the opening and closing of the plug during the rivet repair.
The report raises questions about who initially installed the bolts and why the door's opening at Renton to correct the rivets was not properly documented, US aviation safety expert John Cox said.
"When was the last time those bolts were installed? Did Spirit not install them and then when Boeing opened it the guys didn't realise that they didn't have the bolts? Or did Boeing not install them? That is something that I don't think we have an answer for yet."
Boeing said it has "implemented a control plan to ensure all 737-9 mid-exit door plugs are installed according to specifications."
The panel was found in a backyard in a suburb of Portland, Oregon, but the NTSB did not recover the bolts. The agency also did extensive tests and analysis to determine if they had been present before the crash or had come undone during the incident, it said.
A photo in the report shows three visible locations where bolts are missing, with the fourth location covered by insulation.
The incident has prompted regulators and politicians to ratchet up oversight of the jet manufacturer. The FAA in late January barred Boeing from expanding production of its 737 MAX planes due to the quality issues.
"I certainly agree that the current system is not working, because it's not delivering safe aircraft," FAA Administrator Mike Whitaker told politicians on Tuesday. "So we have to make changes to that."
18°C