To adapt an old Oscar Wilde quote: To lose one aircraft may be regarded as a misfortune. To lose two looks like carelessness.

So what to make of a third Boeing 737 Max suffering a major issue in recent years? Flying at 16,000 feet shortly after taking off in Oregon on January 5, Alaska Airlines Flight 1282 was still climbing when part of the plane’s body detached, leaving passengers looking out at clear air. The incident raises serious concerns about the viability of this type of plane and the industry’s method of assuring aircraft safety.

The plane involved was Boeing’s model 9 737 Max—an aircraft a generation on from the model 8s involved in the 2018 and 2019 Boeing crashes that killed 346 people, and which led to nearly 400 Boeing 737 Max 8s being grounded in early 2019 for over 18 months.

Initial findings suggest this year’s incident may have been caused by loose bolts and “quality control issues” with the part that came loose—a plug that had been attached to the plane to fill an unused door hole.

On January 6, the US Federal Aviation Administration (FAA) grounded approximately 171 of the Boeing 737 Max 9 aircraft operating worldwide, requiring immediate and enhanced safety inspections. These included checking door plugs of the type installed on the Alaska Airlines plane, alongside all components and fasteners for those plugs. On January 9 the FAA said all 737 Maxes with door plugs would remain grounded until the FAA decreed they were safe to return to flight. (Boeing has delivered 214 737 Max 9 jets in total worldwide, but 43 are not under the FAA’s jurisdiction.)

Subsequent reporting appears to indicate similar door plug problems on other model 9s. A photograph shared on social media purportedly showed one of United Airlines’ model 9 fleet with screws that weren’t fully screwed into place on door plugs.

When contacted by WIRED, Boeing spokesperson Jim Proulx declined to comment on this, citing an ongoing investigation by the National Transportation Safety Board (NTSB). “Safety is our top priority, and we deeply regret the impact this event has had on our customers and their passengers,” Boeing said in a January 6 statement.

Robert Mann Jr., an independent aviation analyst, wonders if the latest issues with the model 9 are instead related to the supplier or the plane’s manufacturing. He believes the bolt anomalies depicted in the photo, which was shared on X by an editor at Airline Weekly, are unacceptable. “If I found that on my car, I’d be livid, and it would make me wonder: What else might be there that’s problematic?”

Bjorn Fehrm, an analyst at the aviation industry publication Leeham News, agrees that the apparent overlooking of the tightening of these bolts is significant. “It’s a big issue,” he says. However, as far as the Alaska Airlines incident is concerned, he believes that if the screws had not been fully tightened, it would have been “inconsequential.” These bolts aren’t designed to hold in a door plug, he says.

Spirit AeroSystems, the Wichita-based aerospace manufacturer that manufactured the door plug that blew out on the Alaska Airlines flight, declined to comment on the incident. However, in a statement published on its website, Spirit says its “primary focus is the quality and product integrity of the aircraft structures we deliver.”

The company’s parts have caused issues for Boeing in the past. The Seattle Times reported back in October on defects in Spirit components that contributed to months-long delayed deliveries of Boeing 787 aircraft. Tom Gentile, the then CEO of Spirit, resigned following these and other production errors by the company.

But Fehrm hypothesizes the blowout may have been due to alleged oversights that happened after Spirit had added the door plug, once Boeing retook ownership of the plane. Fehrm claims Boeing uses the door in question to access parts of the plane during its checks ahead of the aircraft being cleared to fly. And so, in his opinion: “Someone has taken away the bolts, opened the door, done the work, closed the door, and forgot to put the pins in.”

In other words, he is leaning toward processes being at fault, not the plane’s design. This, though, raises concerns about the way plane safety checks are conducted.

In theory, in the US the FAA checks aircraft for their airworthiness, granting them certification to fly safely. Aircraft designs are studied and reviewed on paper, with ground and flight tests taking place on the finished aircraft alongside an evaluation of the required maintenance routine to keep a plane flightworthy.

In practice, these reviews are often delegated to third-party organizations that are designated to grant certification. Planes can fly without the FAA inspecting them first-hand. “You won’t find an FAA inspector in a set of coveralls walking down a production line at Renton,” says Tim Atkinson, a former pilot and aircraft accident investigator and current aviation consultant, referring to Boeing’s Washington state–based 737 factory.

The FAA relies on third parties because it’s already overstretched and needs to focus on safety-critical new technologies that push forward the latest innovations in flight. “It can’t [check all aircraft itself], because you’re producing 30 to 60 aircrafts a month, and there are 4 million parts in an aircraft,” says Fehrm.

“Designated examiners have always been part of the landscape,” says Mann, but he believes the latest series of events add to existing questions around whether this is the right approach. On the other hand, there are currently no practical alternatives, he says.

The plane in the Alaska Airlines incident was granted an airworthiness certificate on October 25, 2023, and issued with a seven-year certificate by the FAA on November 2. FAA records do not include who granted the certificate on behalf of the FAA, and the administration declined to identify the organization or individual who approved the plane’s airworthiness. The plane’s first flight took place in early November.

With this being a third major and potentially life-threatening incident for Boeing in little over five years—all involving a single type of aircraft—the company’s status has taken a hit.

There used to be an old saying among pilots, says Atkinson: “If it ain’t Boeing, I ain’t going.” He believes that reputation has diminished with the 737 Max issues, and with it, Boeing’s value. Its share price dropped 8 percent on January 8, the first day of trading after the incident. Citi analyst Jason Gursky estimates delays resulting from those 171 planes being grounded by the FAA will cost Boeing $2.3 million every day the issue lasts.

Airlines that have pulled 737 Max 9s from service have canceled some flights, and dragooned over planes into service to replace the missing 737 Maxes. The challenges in rousting enough planes to cover the absences highlight how beholden the airline industry is to the big two manufacturers: Airbus and Boeing. “The 737 Max is such an important product,” says Graham Braithwaite, professor of safety and accident investigation at Cranfield University in the UK. “Not just to Boeing, but globally, in terms of how many airlines depend on it.”

So what happens now? “Presuming this is limited, and presuming the issues are not judged to be design-oriented, I think this comes down to another major black eye for a number of people in the supply and production chain,” says Mann.

Whether it has a more meaningful impact on confidence in this type of plane, he’s less certain about. “We’ve had lots of airplanes that have had problems, and lots of maintenance practices that have led to problems in the past. But by and large, these things have all become footnotes in quarterly financial statements.”

That’s a forecast Atkinson agrees with. The airline industry regulates by counting tombstones, he says. “No one’s died. There’s massive reputational damage, but the right people are asking questions.”