Investigating why an Alaska Airlines Boeing 737 MAX 9 experienced a mid-air blowout of an emergency door plug, the US National Transportation Safety Board (NTSB) has classified the 5 January event as “an accident” not an incident, and acknowledged the terror and psychological injury experienced by those on board the flight from Portland, Oregon to Ontario, California.

“We don’t often talk about psychological injury but I’m sure that occurred here,” NTSB chair Jennifer Homendy told reporters during a press briefing last night as the NTSB launched its investigation into what transpired on board Flight 1282, and as harrowing videos and images of the event circulated on social media.

“So, on behalf of the National Transportation Safety Board, I’d like to extend our deepest sympathies to those that experienced what I imagine was pretty terrifying,” said Homendy.

Noting that the NTSB is not aware of any serious injuries resulting from the accident but is aware of minor injuries, Homendy didn’t mince words when she said that the scene on board, as relayed to her by flight crew and others, was “chaotic” and “very loud” after the left-side, mid-cabin emergency door plug, located aft of the wings, “departed the airplane resulting in rapid decompression” and indeed in some damage to nearby seats. Thankfully, no passengers were seated next to the door plug in question.

Carrying 171 passengers and six crew members, the aircraft was operating at around 16,000 ft and was around ten minutes out from Portland International Airport when the door plug detached, she said. “Fortunately,” added Homendy, “they were not at cruise altitude” when passengers would have been up and out of their seats to use the lavatories, and cabin crew members would have been attending to passengers.

 We could have ended up with something so much more tragic and we’re really fortunate that that did not occur here.

She assured that at any point in its investigation, the NTSB can issue an urgent safety recommendation “to address potential issues early on”.

The US Federal Aviation Administration — which regulates all aspects of civil aviation and is participating in the NTSB probe alongside Boeing, the airline and crew unions — has already taken initial action, yesterday issuing an Emergency Airworthiness Directive (EAD) that grounds for inspection any 737 MAX 9 aircraft “certificated in any category with a mid-cabin door plug installed”.

A total 171 aircraft worldwide are affected by the EAD, said the FAA. Its grounding came after Alaska Airlines and fellow US-based MAX 9 operator United Airlines took the initiative to start voluntarily grounding aircraft for inspections, resulting in associated delays and cancellations.

“We are working with the FAA to ensure that our inspections meet their detailed requirements and comply with the EAD, but this process will take more time,” warned Alaska yesterday after the EAD dropped.

Other MAX 9 operators including Panama’s Copa Airlines and Turkish Airlines are also conducting inspections.

Though the FAA’s EAD was adopted this morning by the European Union Aviation Safety Agency (EASA), the agency said it doesn’t appear that any EASA Member State airlines currently operate aircraft in the relevant configuration.

High density 737 MAX 9 twinjets — indeed anything certified at 215-220 passengers — requires that the mid-cabin emergency door be operational, explained Homendy during the NTSB media briefing. The Alaska MAX 9 emergency door involved in this accident did not need to be activated because this particular aircraft, with just 178 seats on board, is certified for up to 189 passengers, and given the law’s 189-passenger threshold, “Alaska would not have to have emergency exit doors at that location in the aircraft.”

Instead, the space is plugged.

(Activating and deactivating emergency doors is not a novel concept to Boeing. Airbus previously explained to Runway Girl Network how it can change the location, layout and number of emergency exit doors on the A321neo to facilitate high-density layouts.)

“I will say one good thing on this aircraft is there is an identical door plug just on the other side, so there is a left one and a right one,” Homendy added in reference to the Alaska 737 MAX 9. “We are going to be able to look at the right one, which is fully intact, and see what that one looks like and compare it.” The plug blew off in-flight, but has since been recovered in an area neighborhood.

In addition to the FAA, parties assisting the NTSB in its probe include Boeing, Alaska Airlines, the Air Line Pilots Association (ALPA) and the Association of Flight Attendants.

Asked by a journalist if the NTSB thinks there is an overall problem with the Boeing 737 MAX — which was previously grounded due to two fatal crashes related to design flaws, particularly around flight control software — Homendy said: “At this time, no” but she assured that the NTSB will “go where the investigation takes us”.

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Featured image of Alaska Airlines MAX 9 safety card credited to Jason Rabinowitz