The US Department of Justice (DOJ) has opened a criminal investigation into the blowout of a “door plug” on a Boeing 737 MAX plane operated by Alaska Airlines that departed from Portland, Oregon, bound for Ontario, California, on January 5.

The plane was climbing and had reached 15,000 feet when the panel in an unused door opening in the fuselage was sucked out of the aircraft, causing the cabin to depressurize and oxygen masks to drop, before the crew turned the plane around and made a remarkable emergency landing at Portland International Airport.

The Wall Street Journal first reported the DOJ investigation on Saturday, based on documents and statements provided by unnamed individuals. The report said investigators had contacted passengers and crew members, including pilots and flight attendants, who were on Alaska Airlines Flight 1282 on January 5.

A statement from Alaska Airlines on the matter said: “In an event like this, it’s normal for the DOJ to be conducting an investigation. We are fully cooperating and do not believe we are a target of the investigation.”

The Journal report said that “investigators with the Transportation Department’s Inspector General’s office in recent weeks have been seeking to interview Federal Aviation Administration officials in the Seattle area who oversee Boeing’s manufacturing.” It also said that Alaska Airlines passengers, who were on board during the January 5 door plug accident, are being notified that they are potential crime victims in the case.

The new criminal investigation will “inform” the DOJ’s review of whether Boeing had “complied with an earlier settlement that resolved a federal investigation following two fatal 737 MAX crashes in 2018 and 2019,” the Journal report said. Two Boeing 737 MAX planes suddenly nosedived and crashed—Lion Air Flight 610 in Indonesia on October 29, 2018 and Ethiopian Airlines Flight 302 on March 10, 2019—and killed a combined total of 346 people.

In its investigation into these disasters, the DOJ held Boeing responsible for how it communicated with the Federal Aviation Administration (FAA) about a new 737 MAX flight control system that caused the fatal nosedives. Boeing said during the investigation that two former employees had misled the FAA about the training pilots would need to be able to properly operate the plane’s automated Maneuvering Characteristics Augmentation System (MCAS).

In January 2021, Boeing reached a $2.5 billion settlement with the DOJ in which the largest plane manufacturer in the US was permitted to avoid prosecution on a criminal charge of defrauding the US government in exchange for cooperation with ongoing federal investigations of the company’s operations.

The Journal report says:

If the Justice Department finds that Boeing violated the terms of the 2021 settlement, the company could face prosecution on the original count of defrauding the US. Alternatively, the government could seek to extend the probationary, three-year agreement that requires Boeing to update the Justice Department on its compliance improvements.

As the DOJ’s criminal investigation proceeds, it is likely that Boeing will stop cooperating with the National Transportation Safety Board (NTSB) in the investigation into the technical cause of the door plug blowout incident. This is precisely what happened during the investigation into the 2018 and 2019 fatal nosedive crashes. The company was then permitted to leverage its refusal to cooperate with the FAA and NTSB investigations as a bargaining chip in negotiations over the non-prosecution deal with the DOJ.

As the Journal reported, “Criminal probes can complicate parallel aviation safety investigations.” Last Wednesday, the NTSB expressed worry that the DOJ’s involvement could chill cooperation with its probe into the door plug blowout.

A day later, the NTSB said that Boeing had not turned over critical records that show the specific steps in the assembly line for the 737 MAX-9 last fall when employees removed bolts that hold the door plug in place. NTSB investigators believe that these bolts were not reinstalled before the plane left the Boeing factory in October 2023.

The plane in question flew 150 commercial flights without incident before the midair blowout occurred. During testimony before the Senate Commerce Committee on March 6, NTSB Chairwoman Jennifer Homendy said:

Boeing has not provided us with the documents and information that we have requested numerous times over the past few months, specifically with respect to opening, closing and removal of the door and the team that does that work at the Renton [Washington] facility.

Boeing has said it is cooperating fully with the investigation and the documentation in question has not been provided to the NTSB because it does not exist. Responding to Homendy’s congressional testimony, Boeing issued a statement saying, “if the door plug removal was undocumented there would be no documentation to share.”

However, Homendy also said that NTSB efforts to interview the Boeing employees involved in the door plug removal, who would have been handling the bolts required to reinstall it, have been blocked by the company. She said, “There is one team—one team—that deals with the doors” and called it “absurd” and “really disappointing” that the NTSB still does not have the names of 25 employees and a manager on the team.

The midair blowout in January was the start of a series of non-fatal airline accidents in recent weeks:

• On Sunday, media outlets reported that two pilots of an Indonesian aircraft carrying 157 people fell asleep midflight, causing the plane to veer off its designated path, according to a preliminary report by the country’s transportation safety authority. The pilots were operating a Batik Air flight on January 25 when they both fell asleep for approximately 28 minutes. The report said, “Several attempts to contact BTK6723 had been made by the Jakarta ACC, including asking other pilots to call the BTK6723. None of the calls were responded to by the BTK6723 pilots.”
• On Friday, United Airlines Flight 2477 ran off the taxiway into a grassy area in Houston, Texas. Shortly after landing at 8:00 a.m., the 737 MAX plane veered into the grass on a turn. No one was hurt, and the passengers deplaned onto a set of mobile stairs. They were transported by bus to the airport terminal.
• On Thursday, a tire flew off of a United Boeing 777-200 plane just after take-off from San Francisco on a flight to Osaka, Japan. The 777 plane had 249 people on board. It diverted to Los Angeles International Airport and landed without incident. The falling tire damaged at least one car in an airport parking lot.
• On Monday, an engine failed on a United Airlines flight from Houston to Fort Myers, Florida. Flames shot out from the jet engine shortly after takeoff, forcing the crew to turn the plane around for an emergency landing in Houston. Passengers reported that the plane shuddered and shook, and popping noises could be heard inside the cabin. It was later determined that the engine ingested bubble wrap that had been left on the runway.