Boeing jetliner that suffered inflight blowout was restricted because of concern over warning light

The Boeing jetliner that suffered an inflight blowout over Oregon was not being used for flights to Hawaii after a warning light that could have indicated a pressurisation problem lit up on three different flights.

Alaska Airlines decided to restrict the aircraft from long flights over water so the plane “could return very quickly to an airport” if the warning light reappeared, Jennifer Homendy, chair of the National Transportation Safety Board, said on Sunday.

Shares of The Boeing Co. tumbled 9 per cent at the opening bell on Monday, the first day of trading since the incident occurred. Shares of Alaska Airlines slid 4 per cent and Spirit AeroSystems, which builds the fuselage for Boeing’s 737 Max, plunged 14 per cent.

Homendy cautioned that the pressurisation light might be unrelated to Friday’s incident in which a plug covering an unused exit door blew off the Boeing 737 Max 9 as it cruised about 4.8 kilometres over Oregon.

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The warning light came on during three previous flights: On December 7, January 3 and January 4 — the day before the door plug broke off. Homendy said she didn’t have all the details regarding the December 7 incident but specified the light came on during a flight on January 3 and on January 4 after the plane had landed.

The NTSB said the lost door plug was found Sunday near Portland, Oregon, by a school teacher — for now, known only as Bob — who discovered it in his backyard and sent two photos to the safety board. Investigators will examine the plug, which is 66 by 121 centimetres and weighs 28.5kg, for signs of how it broke free.

Investigators will not have the benefit of hearing what was going on in the cockpit during the flight. The cockpit voice recorder — one of two so-called black boxes — recorded over the flight's sounds after two hours, Homendy said.

At a news conference on Sunday night, Homendy provided new details about the chaotic scene that unfolded on the plane. The explosive rush of air damaged several rows of seats and pulled insulation from the walls. The cockpit door flew open and banged into a lavatory door.

The force ripped the headset off the co-pilot and the captain lost part of her headset. A quick reference checklist kept within easy reach of the pilots flew out of the open cockpit, Homendy said.

The plane made it back to Portland, however, and none of the 171 passengers and six crew members was seriously injured.

Hours after the incident, the FAA ordered the grounding of 171 of the 218 Max 9s in operation, including all those used by Alaska Airlines and United Airlines, until they can be inspected. The airlines were still waiting Sunday for details about how to do the inspections, but the cancellations of flights involving Max 9 aircraft at both airlines have begun.

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Early on Monday, Alaska Airlines was forced to cancel 20 per cent of all flights, 141 in all. United cancelled 221 flights, or 8 per cent of its total flights scheduled for Monday.

Alaska Airlines, which has 65 Max 9s, and United, with 79, are the only US airlines to fly that particular model of Boeing’s workhorse 737. United said it was waiting for Boeing to issue a “multi-operator message,” which is a service bulletin used when multiple airlines need to perform similar work on a particular type of plane.

Boeing was working on the bulletin but had not yet submitted it to the FAA for review and approval, according to a person familiar with the situation. Producing a detailed, technical bulletin frequently takes a couple days, said the person, who spoke on condition of anonymity to describe a matter that the company and regulators have not publicly discussed.

Boeing CEO Dave Calhoun called for a companywide webcast on Tuesday to talk about the incident with employees and senior leadership.

“When serious accidents like this occur, it is critical for us to work transparently with our customers and regulators to understand and address the causes of the event, and to ensure they don’t happen again,” Calhoun wrote in a message to employees Sunday. “This is and must be the focus of our team right now.”