“Passengers in the seats immediately adjacent, or in other seats around it who weren’t wearing a seatbelt could have been sucked out of the aircraft”, explained Tim Atkinson, an aviation consultant and former aircraft accident investigator.
“I guess the worst case could be you lose a row full of people and a couple of others standing nearby as well.”
The temperature in the aircraft would also have dropped dramatically. Air at such altitudes is typically very cold, around -57C (-71F).
Passengers and crew would have been reliant on emergency oxygen. Without it they would have quickly lost consciousness.
Jennifer Homendy, chair of the US National Transportation Safety Board (NTSB), said it was “very, fortunate here that this didn’t end up in something more tragic”.
In 2018, exactly such an incident occurred to an older model of Boeing 737 being operated by Southwest Airlines. Debris from an engine failure broke one of the cabin windows while the plane was travelling at 32,000ft.
The aircraft suffered a sudden decompression, and one passenger was partially sucked out of the window. She died as a result of her injuries.
The immediate concern in this case is whether what happened to Flight 1282 could happen to other aircraft. The door in question is meant to be securely bolted to the fuselage using four bolts. The aircraft was only two months old, meaning simple wear and tear is unlikely to have been a factor.
That is why Alaska Airlines initially chose to ground its fleet of 737 Max 9s.
The US regulator, the Federal Aviation Administration (FAA) followed suit, temporarily grounding 171 aircraft for inspections.
“It could be design, it could be a manufacturing defect, or a combination of the two. Or it could be something else, something unknown”, said Mr Atkinson.
The NTSB has revealed that pilots had seen a pressurisation warning light come on during previous flights, and that the plane had been restricted from making long journeys over water as a result.
It has warned, however, that this might not be connected to the incident itself.
An expert on 737 aircraft suggested to the BBC that the repeated appearance of such a warning light would certainly have been taken seriously. In addressing it, airline technicians would have followed the aircraft’s maintenance manual – a document drawn up by Boeing but signed off by the regulator.
He added that there are also indicator lights on the flight deck to warn when individual doors are not properly closed, but because the door that went missing was not in use, that particular warning light would not have been operational.
The investigation is expected to involve both Boeing and its supplier, Spirit AeroSystems, which actually manufactured the door.
For Boeing, there is an additional problem.
The aircraft involved in the incident was a variant of the 737 Max, the latest generation of Boeing’s 737 workhorse. The plane, designed to be much more fuel efficient than previous models, has been a hit with airlines. But its safety record has been badly tarnished.
In late 2018 and early 2019, two aircraft were lost in near identical accidents, off the coast of Indonesia and outside the Ethiopian capital Addis Ababa.
A total of 346 people were killed. Both crashes were caused by flawed flight control software, which ultimately forced the planes into catastrophic dives, despite the best efforts of the pilots.
