Federal Aviation Administration inspectors were starting to probe Boeing 737 Max 9 planes operating domestically to find the cause of a fuselage blowout on Jan. 5 on an Alaska Airlines flight from Portland, Ore., to Ontario, Calif.
The grounding affected 65 planes belonging to Alaska (ALK) -) and 78 planes operated by United Airlines (UAL) -).
The groundings total 171 planes and also affected planes operated by Turkish Airlines, Panama's Copa Airlines, and Aeromexico, the Mexican carrier, Reuters reported.
It was not clear if other airlines are affected by the FAA order.
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Alaska cancelled 163 flights on both Saturday and Sunday and saw at least 394 flight delays. United cancelled 256 flights on Sunday on top of 125 on Saturday. There were 1,171 United flight delays over the two days, according to FlightAware.com.
More cancellations were expected Monday for both carriers.
The groundings of the relatively new model of Boeing's passenger airliner were prompted after Alaska flight 1282 from Portland experienced a fuselage blow-out Friday evening. The plane was able to return quickly to Portland.
Miraculously, there were only minor injuries from the blowout on Alaska Flight 1282, but passengers later described a loud explosion, wind whooshing through the cabin, followed by the deployment of oxygen masks in the cabin.
One passenger told The New York Times, "I thought I was going to die."
The flight had 171 passengers and six crew members.
The incident occurred when the plane reached an altitude of about 16,000 feet, about three miles above the ground, on its way to its cruising altitude for the two-and-a-half hour flight. Commercial airline flights typically cruise at about 30,000 feet.
Passengers said the missing section of the plane was the plug put in to replace an aft door on the left side.
The window seat next to the plug was not occupied when the plug broke away from the plane Friday evening.
However, a teenage boy and his mother occupied the middle and aisle seats.
The boy's shirt was torn off, and some passengers suggested he was nearly pulled out as winds howled in the cabin, according to the Oregonian newspaper. But his mother pulled him back in. The cabin crew moved mother and son elsewhere.
Reports said passengers were silent as the plane made its descent but erupted in applause when the plane touched down.
Afterward, passengers posted videos of the experience on X, formerly Twitter, and elsewhere.
Alaska's seating configuration for the 737 9 is not dense enough to require the mid-aft cabin exit, according to a post by Flightradar24, which tracks airline activity, on X, formerly Twitter.
So, the door is deactivated and replaced by the plug secured by four bolts. Standard sidewall paneling is used on the interior. "To a passenger, it’s just like any other seat," the post said.
Other airlines also use plugs.
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Carriers that do need the exit include Ryanair, the Irish carrier that offers ultra-low fares in Europe and pack seats tightly with passengers.
What was still not clear Sunday was why or how the plug broke free. The plug was believed to landed in the southwest suburbs of Portland, and investigators were searching for it on Sunday.
The plugs are installed and bolted in place when the fuselages are built. Spirit AeroSystems builds the fuselages in Wichita, Kan. Spirit AeroSystems was once part of Boeing but was sold off in 2005.
Alaska's plane was quite new, having been certified in November, according to the F.A.A. registry of aircraft, the New York Times reported. It entered commercial service that month and has since logged 145 flights, according to Flightradar24, a flight tracking site.
Boeing’s Max aircraft have a troubled history. After two crashes of Max 8 jets killed hundreds of people within several months in 2018 and 2019, the Max was grounded around the world, The New York Times reported.
A heavy workload
Airlines don't let planes sit idle. The plane used on Flight 1282 had been flown from San Diego to New York on Thursday and then to Portland on Friday before starting its trip to Ontario.
Alaska and Southwest Airlines (LUV) -) are among a number of carriers that use only planes from the Boeing 737 family.
Alaska, based in Seattle, typically gets high grades for customer service. The stock closed up 3.1% at $37.95 on Friday before the incident.
Boeing shares were up 1.7% on Friday to $249. They fell 4.5% in the first week of January, however, after rising 36.8% in 2023.
