An incident on an Alaska Airlines flight where part of the fuselage tore away has again put the spotlight on Boeing’s newest and top-selling model, the 737 Max. Here we look at what happened and what it might mean for Boeing and its 737 Max.
What exactly happened this time?
A door plug detached from the jet minutes after takeoff from Portland, Oregon – effectively leaving a gaping door-sized hole in the wall of the main passenger cabin. The plane made an emergency landing, with all passengers and crew safe. Accident investigators said that the consequences of the incident – which occurred at a relatively low altitude of 16,000 feet with all passengers still strapped in, and no one sitting in the seat adjacent to the rupture – could have been much more serious.
What caused it and what are the authorities doing?
The cause is so far unknown – but now that the missing door plug, which landed in a teacher’s back yard, has been located, US investigators hope to make progress. Boeing 737 Max 9 planes with similar door plugs have been grounded on order of the US Federal Aviation Administration, pending inspections to check their safety. Investigators said that an auto pressurisation fail light on the same Alaska Airlines aircraft had triggered three times in its two months in service, leading the airline to decide to restrict the plane from long flights over water.
Are all 737 Max planes affected? What is the difference between the models?
No. This is the 737 Max 9, a longer version than the most common version, the Max 8. It is capable of carrying 220 passengers, a number that would require it to have an additional emergency exit in the middle of the cabin. However, several airlines, including Alaska, have not requested interiors with the maximum number of seats – meaning that the door is instead plugged.
Who operates the 737 Max 9?
Only 11 airlines have so far ordered this variant, and the majority of flights are operated by just two carriers in the US: United Airlines has 79 737 Max 9s in its fleet, all of which are configured with door plugs. Alaska has 65 of the same model, again with door plugs. Aeromexico and the Panamanian carrier Copa are the next biggest, and mostly with plugged variants, while no other airline owns more than five such planes. According to data from the analysts Cirium, almost 20,000 flights worldwide were scheduled this month on 737 Max 9s.
Is it only 737 Max 9s that have such door plugs?
No, and investigators do not yet know where the fault lies. But aviation regulators fear that whatever fault developed might be repeated in similar models of the same production or assembly lines. The fuselage parts are manufactured and installed at Spirit AeroSystems, Boeing’s largest supplier, and normally reinstalled by Boeing during the production process. The Alaskan 737 Max 9 whose door plug blew off was only two months old.
Why is the 737 Max so well known?
The Boeing 737 was long the world’s bestselling aircraft, a single-aisle plane designed to operate short-haul flights, and the 737 Max was the newest iteration. But while only aviation enthusiasts might know or care what model of plane is being flown, the 737 Max hit the headlines after two fatal crashes soon after its introduction into service in 2018, at Lion Air and then Ethiopian Airlines, killing 346 people onboard. And, unusually, it became clear that the aircraft’s own design flaws were to blame.
Surely all that has been ironed out?
Yes – the plane was grounded worldwide, modified, and then intensively retested by regulators globally before recertification. Huge orders have been placed by carriers such as Ryanair, which ordered another 300 of the 737 Max 10 model last year. Airlines love the savings promised from greater fuel efficiency for each passenger. But any problems around the Max are likely to provoke more scrutiny, headlines and unease than other models.
So have there been other concerns?
Indeed. It is barely a week since Boeing urged its airline customers to check for loose or missing bolts in the rudder control after two instances were identified, “out of an abundance of caution”, according to the manufacturer. Last year it emerged that it had identified faults in fuselage parts supplied by Spirit, holding up production of more planes.
