FAA temporarily grounds some Boeing planes after Alaska Airlines jet returns with big hole

A left door plug that expelled from an Alaska Airlines flight had disengaged from the fuselage, "allowing it to blow out," the National Transportation Safety Board said late Monday, offering further details on the midflight blowout.

The flight was forced to return to Portland, Oregon, shortly after takeoff when a section of the fuselage separated from the plane. Social media posts showed a hole in the side of the aircraft where the section of fuselage blew out.

According to Alaska Airlines, flight 1282 was en route to Ontario, California, from Portland when the incident occurred. The plane returned to Portland with all passengers and six crew members, who deplaned safely.

The Federal Aviation Administration is now grounding approximately 171 Boeing 737 Max 9 jets as a result of the incident. The required inspections will take around four to eight hours, the FAA said in a statement on X, formerly Twitter.

"This emergency (airworthiness directive) was prompted by a report of an in-flight departure of a mid cabin doorplug, which resulted in a rapid decompression of the airplane. The FAA is issuing this AD to addressthe potential in-flight loss of a mid cabin door plug, which could result in injury to passengers andcrew, the door impacting the airplane, and/or loss of control of the airplane," the agency's order said. "This AD prohibits further flight of affected airplanes, until the airplane is inspected and all applicable corrective actions have been performed."

NTSB says it's unclear if bolts for door plug were properly attached

The missing door plug, which was discovered in a backyard in Portland on Sunday, is a key piece in the investigation of what happened during the flight.

During Monday night's news conference, NTSB aerospace engineer Clint Crookshanks said it is uncertain if bolts for the door plug were properly attached or had even been installed. The NTSB said lab testing would reveal if the bolts were in place.

Earlier Monday, United Airlines and Alaska Air said they had found loose parts on numerous grounded Max 9 jets.

NTSB Chair Jennifer Homendy also noted during the conference that there are currently "no indications" that activation of the air pressurization warning light correlated with the expulsion of the door plug and the rapid decompression of the plane.

During the plane’s “explosive decompression," the cockpit door was flung open and passengers described a chaotic, loud, and violent scene as the winds blew through the plane. Homendy said Monday that the cockpit door was designed to open during rapid decompression but no crew on board were informed.

Concerns had been raised over the plane's pressurization after federal officials reported that warning lights had gone off on three separate flights on Dec. 7, Jan. 3, and Jan. 4 — the day before the incident.

Alaska Airlines, Boeing also investigating incident

“My heart goes out to those who were on this flight – I am so sorry for what you experienced. I am so grateful for the response of our pilots and flight attendants. We have teams on the ground in Portland assisting passengers and are working to support guests who are traveling in the days ahead,” Alaska CEO Ben Minicucci said in a statement. “

Minicucci said the airline is working with Boeing, the plane manufacturer, to “understand what occurred.”

Alaska was reporting 52 canceled flights, or about 7% of its schedule just before 7:30 a.m. ET on Saturday.

It’s the second high-profile aviation incident of 2024, coming just days after a Japan Airlines plane struck a Japanese Coast Guard aircraft on the runway at Tokyo Haneda Airport. The crash killed five crew members on the Coast Guard plane, but despite a fire that largely consumed the Japan Airlines Airbus A350, all passengers and crew aboard the commercial flight were able to evacuate safely.

Zach Wichter is a travel reporter for USA TODAY based in New York. You can reach him at zwichter@usatoday.com

This article originally appeared on USA TODAY: Boeing 737 Max 9 grounding by FAA after Alaska Airlines incident