United Airlines and Alaska Airlines said Monday they found spare parts on some of their Boeing 737 Max 9 planes after a fuselage panel exploded during a flight in Alaska on Friday, adding to growing safety concerns over the Max 9.
The revelations follow reports that Alaska Airlines was warned three times before Friday’s flight about pressure problems in the plane’s cabin. These warnings were significant enough that the airline decided the plane, a Max 9, could no longer be used on flights to Hawaii.
United said Monday it found loose bolts in the panels, known as door plugs in the industry, after it began removing seats and sidewall coverings for inspections this weekend. The caps are placed where an emergency exit door would be if a plane had more seats. Alaska Airlines said later in the day that technicians preparing Max 9 planes for inspections after the in-flight emergency had discovered “loose hardware” in some cases.
A door jam suddenly flew off the Alaska Airlines plane Friday as cabin pressure dropped about 10 minutes after takeoff from Portland, Ore., subjecting passengers to howling wind and forcing pilots to return quickly to the airport. The door stopper, phones, toys and other personal items all came out of the hole in the side of the plane and fell across the city.
Airlines have canceled hundreds of flights as they prepare to inspect nearly 200 planes that will be grounded until regulators and company officials decide they are safe. Alaska Airlines used 65 Max 9 packages, or about 20% of its fleet, and United used 79, more than any other airline and about 8% of its fleet, according to Cirium, an aviation data provider. Some passengers’ travel plans may be disrupted for several days.
The Federal Aviation Administration sent instructions to airlines Monday morning on how to conduct inspections. United said late in the day that it was still waiting for additional approval from the FAA before it could begin inspections. Alaska said it was waiting for guidance from Boeing and the FAA to begin. But technicians from both airlines have nevertheless started preliminary inspection work, they said.
Officials led by the National Transportation Safety Board are focusing on, among other things, installation and inspection of the plug.
“I think investigators are going to focus on the manufacturing process of this particular plane,” said Jeff Guzzetti, a former NTSB and FAA investigator. “How was this door stopper installed or who installed it?”
The door was originally installed by Spirit AeroSystems, which makes the body for the 737 Max and other planes. Investigators said they were looking into whether any work had been done on or near the door since the plane entered service in November.
Jennifer Homendy, chairwoman of the NTSB, said investigators have a lot of work to do, including inspecting the cork, which was recovered from a yard near Portland. The committee will also examine a plug that remained intact on the other side of the plane, interview flight crews and passengers, review maintenance records and repair logs, and conduct laboratory analyzes of plane parts .
Investigators could also determine whether the installation of wireless Internet equipment on the plane by a contractor, AAR, between Nov. 27 and Dec. 7 played a role in pressurization problems that emerged after the work was completed. In a statement Monday, AAR said it “did not perform any work on or near the mid-exit door plugs on this specific aircraft.”
Although no serious injuries were reported, the crash could have been much more catastrophic, especially if the plane had been at a higher altitude, experts say. Ms Homendy said on Sunday evening that the passengers included three babies and four unaccompanied children aged between 5 and 17.
Ms. Homendy said in a brief interview Monday that her team was examining the plane’s flight data recorder to try to determine whether the pressurization warning light could be linked to the door plug. The plan has several backup systems in case one of the pressurization systems fails.
“There may have been a problem with the light or another unit, but there are redundancies in the system,” Ms Homendy said.
Kathleen Bangs, an aviation expert and former airline pilot, said she believed the investigation would reveal a door stopper failure due to the plane’s condition. Typically, explosive decompression incidents occur on older planes with corrosion and metal fatigue, Ms. Bangs said. In this case, she said, the plane was almost new, indicating there was likely a problem with the door plug.
Anthony Brickhouse, a professor of aerospace safety at Embry-Riddle Aeronautical University, said an eruption at a cruising altitude of more than 30,000 feet could have been disastrous. “We could have envisaged a situation where more of the structure could have come loose and a situation where the passengers who were not properly strapped in would have been blown away because the forces would have been so enormous,” he said .
Pressurization begins to affect most commercial planes at about 8,000 feet altitude, said Mr. Brickhouse, who previously investigated aviation accidents on behalf of the safety office. Improper control of air entering and exiting the cabin can cause altitude sickness, or hypoxia, among passengers and crew.
Hypoxia, a condition that develops when the brain is deprived of oxygen, can occur aboard planes without proper pressurization when they begin flying above 10,000 feet or undergo rapid decompression, the FAA says . That’s why flight attendants advise passengers to use drop-down masks in case of rapid decompression, Mr. Brickhouse said.
In a statement, the FAA said the required inspections would focus on caps, door components and fasteners.
“Our teams have worked diligently – with extensive FAA review – to provide comprehensive technical instructions to operators for the required inspections,” said Stan Deal, general manager of Boeing’s commercial aircraft unit, and Mike Delaney , responsible for aerospace safety. in a message to employees of this unit on Monday.
Other airlines offering Max 9 packages are outside the United States, such as Copa Airlines of Panama, Turkish Airlines, and Icelandair. The European Union’s aviation safety agency announcement On Monday, Max 9 planes operating in Europe were not grounded because they had a different configuration.
The FAA previously said it would take four to eight hours to inspect each plane. Inspection of the nearly 200 Max 9 planes in the United States, according to the aviation agency, could take a few days.
Aviation regulators and Boeing said the inspections were unique to the Max 9. The Max 9, along with the more popular Max 8, were grounded for nearly two years after two Max 8 crashes in 2018 and 2019, which killed 346 people.
Federal authorities investigating the incident are also examining what triggered pressurization warnings on the damaged plane during three recent flights. Alaska Airlines employees reset the system and the plane was returned to service, although the airline banned its use on flights to destinations like Hawaii, Ms. Homendy said. She added that it was not yet clear whether the warnings were related to Friday’s accident.
In a statement, Alaska said it could not answer many outstanding questions about the plane and what led to the explosion without approval from the safety board. The airline said it had asked the NTSB to share more information and would do so if allowed. In such investigations, parties are generally limited in what they can share publicly.
Boeing Chief Executive Dave Calhoun plans to hold a company-wide safety meeting Tuesday to discuss the company’s response to the episode and reaffirm its commitment to safety . Boeing is still working to gain approval for the smaller Max 7 and larger Max 10.
Shares of Boeing closed down about 8 percent Monday, and shares of Spirit AeroSystems closed down 11 percent.
J. Edward Moreno reports contributed.