Boeing 737 Max 9: Airlines found loose parts in door panels during jet inspections

An Alaska Airlines jetliner blew out a portion of its fuselage seven minutes after takeoff above Oregon Friday night. The blowout has renewed safety concerns for Boeing. (January 8) Wpc Louver Panels

An Alaska Airlines jetliner blew out a portion of its fuselage seven minutes after takeoff above Oregon Friday night. The blowout has renewed safety concerns for Boeing. (January 8)

Residents of a Portland, Oregon, neighborhood found parts plane parts in their yards after an Alaska Airlines jetliner blew a hole in its fuselage above them. (Jan. 9)

A woman aboard the Alaska Airlines plane that had a hole blown out of its fuselage recounts the experience, including talking to one of the passengers seated on the row where it happened (Jan. 8)

This photo released by the National Transportation Safety Board shows the door plug from Alaska Airlines Flight 1282 on Monday, Jan. 8, 2024, in Portland, Ore. A panel used to plug an area reserved for an exit door on the Boeing 737 Max 9 jetliner blew out Jan. 5, shortly after the flight took off from Portland, forcing the plane to return to Portland International Airport. (National Transportation Safety Board via AP)

In this photo released by the National Transportation Safety Board, NTSB Investigator-in-Charge John Lovell examines the fuselage plug area of Alaska Airlines Flight 1282 on Sunday, Jan. 7, 2024, in Portland, Ore. A panel used to plug an area reserved for an exit door on the Boeing 737 Max 9 jetliner blew out Friday night shortly after the flight took off from Portland, forcing the plane to return to Portland International Airport. (National Transportation Safety Board via AP)

Alaska Airlines N704AL, a 737 Max 9 which made an emergency landing at Portland International Airport after a part of the fuselage broke off mid-flight on Friday, is parked at a maintenance hanger in Portland, Ore., Saturday, Jan. 6, 2024. (AP Photo/Craig Mitchelldyer)

This image from video provided by Elizabeth Le shows passengers near the damage on an Alaska Airlines Boeing 737 Max 9, Flight 1282, which was forced to return to Portland International Airport on Friday, Jan. 5, 2024. (Elizabeth Le via AP)

FILE - The logo for Boeing appears on a screen above a trading post on the floor of the New York Stock Exchange, July 13, 2021. Wall Street is mixed in early trading on Monday. Boeing dragged the Dow lower after one of its jets suffered an inflight blowout. (AP Photo/Richard Drew, File)

National Transportation Safety Board Chair Jennifer Homendy speaks to the media about the investigation of Alaska Airlines flight 1282 in Portland, Ore., Saturday, Jan. 6, 2024. Federal officials on Saturday ordered the immediate grounding of some Boeing 737 Max 9 jetliners until they are inspected after the Alaska Airlines plane suffered a blowout that left a gaping hole in the side of the fuselage. (AP Photo/Craig Mitchelldyer)

Stephanie Shinn from Kenmore waits three hours at this point while her husband waits in line to rebook their flight to Philadelphia after their flight on Alaska Airlines was canceled at Seattle-Tacoma International Airport on Saturday, Jan. 6, 2024, in SeaTac, Wash. (Karen Ducey/The Seattle Times via AP)

Kelvin Lau, left, waits with his family, including daughter Chloe, 3, to rebook a canceled Alaska Airlines flight, Saturday, Jan. 6, 2024, in SeaTac, Wash. (Karen Ducey/The Seattle Times via AP)

An Alaska Airlines Boeing 737-990ER flight 337 from Fort Lauderdale, Fla., lands at Portland International Airport in Portland, Ore., Saturday, Jan. 6, 2024. The FAA has ordered the temporary grounding of Boeing 737 MAX 9 aircraft after part of the fuselage blew out during a flight. (AP Photo/Craig Mitchelldyer)

Alaska Airlines flight 1276, a Boeing 737-900, taxis before takeoff from Portland International Airport in Portland, Ore., Saturday, Jan. 6, 2024. The FAA has ordered the temporary grounding of Boeing 737 MAX 9 aircraft after part of the fuselage blew out during a flight. (AP Photo/Craig Mitchelldyer)

On a personal electronic GPS, Beaverton, Ore., resident Adam Pirkle shows the 14 miles he rode on his bicycle in his neighborhood and around southwest Portland, Ore., Sunday, Jan. 7, 2024, looking for the exit door plug of a Boeing 737 Max 9 that detached shortly after the takeoff of an Alaska Airlines flight on Friday, Jan. 5. The National Transportation Safety Board estimated the piece may have fallen in the area. (AP Photo/Claire Rush)

PORTLAND, Ore. (AP) — Federal investigators say a door panel slid up before flying off an Alaska Airlines jetliner last week, and they are looking at whether four bolts that were supposed to help hold the panel in place might have been missing when the plane took off.

The comments Monday from the National Transportation Safety Board came shortly after Alaska and United Airlines reported separately that they found loose parts in the panels — or door plugs — of some other Boeing 737 Max 9 jets.

“Since we began preliminary inspections on Saturday, we have found instances that appear to relate to installation issues in the door plug — for example, bolts that needed additional tightening,” Chicago-based United said.

Alaska said that as it began examining its Max 9s, “Initial reports from our technicians indicate some loose hardware was visible on some aircraft.”

The findings of investigators and the airlines are ratcheting up pressure on Boeing to address concerns that have grown since the terrifying fuselage blowout Friday night. A plug covering a spot left for an emergency door tore off the plane as it flew 16,000 feet (4,800 meters) above Oregon.

Boeing has called an online meeting for all employees Tuesday to discuss safety.

The company, which has had problems with various planes over the years, pledged to “help address any and all findings” that airlines make during their inspections of Max 9 jets. Boeing has delivered more than 200 to customers around the world, but 171 of them were grounded by the Federal Aviation Administration on Saturday until the door plugs can be inspected and, if necessary, fixed.

The door plugs are inserted where emergency exit doors would be located on Max 9s with more than about 200 seats. Alaska and United have fewer seats in their Max 9s, so they replace heavy doors with the plugs.

The panels can be opened for maintenance work. The bolts prevent the mechanism from moving upward on rollers when the plane is in flight.

During Alaska Airlines flight 1282 on Friday night, roller guides at the top of one of the plugs broke — for reasons the investigators don’t fully understand yet — allowing the entire panel to swing upward and lose contact with 12 “stop pads” that keep the panel attached to the door frame on the plane, NTSB officials said at a news briefing in Portland.

This photo released by the National Transportation Safety Board shows the door plug from Alaska Airlines Flight 1282 on Monday, Jan. 8, 2024, in Portland, Ore. (National Transportation Safety Board via AP)

NTSB Chair Jennifer Homendy said the safety board was investigating whether four bolts that help prevent the panel from sliding up on rollers were missing when the plane took off from Portland or whether they blew off “during the violent, explosive decompression event.”

The interior of the plane suffered extensive damage, but pilots were able to return to Portland and land safely. Officials say there were no serious injuries among the 171 passengers and six crew members.

The lost door panel was found Sunday near Portland in the back yard of a school teacher’s home. NTSB officials said it will be sent to the agency’s lab in Washington, D.C., for detailed study that might help pinpoint why the plug broke loose.

Alaska and United have canceled hundreds of flights since the weekend because of their grounded planes. Alaska has 65 Max 9s, and United has 79. The airlines waited until Monday before Boeing and the FAA completed instructions for how to inspect their planes.

The jet involved in Friday’s blowout is brand-new, having been put in service in November. After a cabin-pressurization system warning light came on during three flights, the airline stopped flying it over the Pacific to Hawaii. Some aviation experts questioned why Alaska continued using the plane on overland routes until it figured out what was causing the pressurization warnings.

Homendy said Monday, however, that NTSB has seen no evidence to link the warnings with the blowout of the door plug.

The Max is the newest version of Boeing’s 737, a twin-engine, single-aisle plane that debuted in the late 1960s and has been updated many times. The 737 has long been a workhorse for airlines on U.S. domestic routes.

Shares of Boeing fell 8% and Spirit AeroSystems, which installs the door plugs on Max jets, dropped 11% on Monday.

Koenig reported from Dallas and Krisher reported from Detroit. Associated Press reporter Terry Spencer in Fort Lauderdale, Florida, contributed to this report.

Boeing 737 Max 9: Airlines found loose parts in door panels during jet inspections | AP News