Boeing 737 history: What you need to know after window blowout terrifies passengers

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Alaska Airlines has grounded its entire fleet of Boeing 737 Max 9 aircraft after a panel blew out from one of the aircraft as it climbed from Portland, Oregon.

The plane, on a routine flight to Ontario near Los Angeles, suffered immediate depressurisation and declared an emergency. All 177 passengers and crew were safe when the aircraft landed back at Portland. But the incident has once again raised questions about an aircraft type that was involved in two fatal crashes.

The Boeing 737, first launched in 1967, is the world’s most successful aircraft – with around 10,000 delivered. But the latest version, the Max, was involved in two terrible tragedies.

On 29 October 2018, a faulty sensor triggered an anti-stall system that caused Lion Air flight 610 to crash shortly after take off from Jakarta. All 189 passengers and crew died.

Less than six months later, Ethiopian Airlines flight 302 from Addis Ababa to Nairobi was lost, along with 157 lives, in similar circumstances.

The plane was grounded worldwide shortly afterwards. After a rigorous redesign and certification, the aircraft is flying again – including for Europe’s biggest budget airline, Ryanair.

What does the latest event mean for passengers? These are the key questions and answers.

What was the cause of the two fatal crashes?

Both tragedies were attributed to software known as the Maneuvering Characteristics Augmentation System (MCAS), which was installed because of the unusual structure of the latest variant of the 737 – with large engines mounted further forward than is usual.

MCAS was intended “to provide consistent handling qualities”. But neither the main safety regulator, the Federal Aviation Administration (FAA) nor airlines that bought the plane were fully informed of the new system.

In both crashes, incorrect data from a faulty sensor caused the software to push the nose of the aircraft down repeatedly while the pilots struggled for control.

Following the Ethiopian Airlines tragedy, the Max was grounded for 20 months while safety enhancements were made. The plane re-entered service in December 2020 and has been flying routinely since then.

What appears to have happened to Alaska Airlines jet?

A panel containing a window blew out of the port side of the Boeing 737 Max 9. The panel fills the space for what is termed a “deactivated mid-cabin exit” – at a position where, if the airline required it, an additional emergency exit could be located between the overwing and aft exits. Instead, a plug is fitted.

Is there any connection between this latest event and the two tragedies?

Not beyond the fact that they were both using the latest version of the Boeing 737. The fatal accidents were due to catastrophically designed software. This latest event is a structural issue.

How serious must it be for Alaska Airlines to ground all its planes?

Ben Minicucci, the airline’s chief executive, said the 65 jets had been grounded as a “cautionary step”. They are expected to return to service in the next few days once inspections are completed.

What does Boeing have to say?

“We are working to gather more information and are in contact with our airline customer. A Boeing technical team stands ready to support the investigation.”

Could the same thing happen to a jet I am travelling on?

Most unlikely. The aircraft Ryanair uses do not have the “deactivated exit” – they have a real emergency exit, which is required to increase the capacity of the plane above the normal 189 limit. Ryanair’s Boeing 737 Max aircraft have a special class, known as the Max 200, but that are based on the Max 8 shell.

Would you step aboard a Boeing 737 Max?

Yes, I have found the aircraft excellent to fly on, and I trust the judgment of the captain and his or her airline.

Simon Calder, also known as The Man Who Pays His Way, has been writing about travel for The Independent since 1994. In his weekly opinion column, he explores a key travel issue – and what it means for you.