US officials have recovered a panel that blew off an Alaska Airlines airliner triggering a partial grounding of Boeing's 737 MAX 9 and sending shares in the planemaker tumbling on Monday.
A door plug tore off on Friday following takeoff from Portland, Oregon, en route to Ontario, California, depressurizing the plane and forcing pilots to turn back.
The plane, with 171 passengers and six crew on board, landed safely.
The U.S. Federal Aviation Administration (FAA) on Saturday ordered the temporary grounding of 171 Boeing MAX 9 jets installed with the same panel, which weighs about 60 pounds (27 kg) and covers an optional exit door.
It was recovered on Sunday by a Portland school teacher identified only as "Bob" in the Cedar Hills neighborhood who found it in his backyard, U.S. National Transportation Safety Board (NTSB) Chair Jennifer Homendy said.
She said she was "very relieved" it had been found having called it a "key missing component" to determine why the accident occurred.
"Our structures team will want to look at everything on the door - all of the components on the door to see, to look at, witness marks, to look at any paint transfer, what shape the door was in when found. That can tell them a lot about what occurred," she said.
The force from the loss of the panel was strong enough to blow open the cockpit door during flight, said Homendy, adding that it must have been a "terrifying event" to experience.
"They heard a bang," Homendy said of the pilots, who were interviewed by investigators.
Homendy said the cockpit voice recorder did not capture any data because it had been overwritten. She again called on regulators to mandate retrofitting existing planes with recorders that capture 25 hours of data, up from the two hours required in the U.S. at present.
Boeing early on Monday shared instructions with airlines for inspecting the 737 MAX 9 fleet, the company confirmed, after 171 MAX planes were grounded by U.S. regulators on Saturday following an accident where a cabin panel ripped off an Alaska Airlines jet while in mid-air.
The instructions, known formally as a multi-operator message, are a key step to allow airlines to complete or certify inspections have been conducted that comply with the Federal Aviation Administration's directive that would allow them to put planes back in service.
"We agree with and fully support the FAA’s decision to require immediate inspections of 737-9 MAX airplanes with the same configuration as the affected airplane," Boeing Commercial Airplanes head Stan Deal said in a letter to employees.
"Our teams have been working diligently – with thorough FAA review – to provide comprehensive, technical instructions to operators for the required inspections," he said. "This morning, our team issued the instructions via a multi-operator message."
The message was delivered to airlines around 3 a.m. Pacific Time (1100 GMT), a source told Reuters, who was first to report that Boeing had sent the instructions.
Boeing's shares fell as much as 8% in pre-market U.S. trade on Monday as investors digested the latest setback for the planemaker.
If the losses hold, the company would lose more than $12.5 billion in value, almost the cost of developing a new plane.
The mishap comes as Boeing and supplier Spirit AeroSystems, which made the panel, grapple with ongoing production setbacks that have hampered recovery from an earlier lengthy 737 MAX safety grounding and wider disruption from the pandemic.
Since the 737 MAX was grounded in March 2019, Boeing shares have fallen by more than 40% while Airbus shares are up 25%.
Spirit Aero shares were down 15.9% in U.S. pre-market trading on Monday. Alaska Airlines shares fell 5% while shares in United Airlines, the only other U.S. airline that operates the jets, dropped 2.8%.
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