The US has ordered the worldwide grounding of 171 Boeing 737-9 aircraft after a window and piece of fuselage blew out midair and forced an emergency landing in Portland, Oregon.

Passengers on Alaska Airlines Flight 1282 said they heard a “bang and whoosh” before oxygen masks dropped and they realised a huge chunk of the plane was missing.

The gaping hole caused the cabin to depressurise before it turned back to Portland International Airport and landed safely with 171 passengers and six crew.

The unusual and frightening incident occurred not long after take-off when the plane had climbed to 4876 metres.

One boy’s shirt was said to have been sucked out of the plane and his mother held onto him in fear he would meet the same fate.

The huge gap near passenger seats. Photo: X (Kyle Rinker)

Passenger Evan Smith told media: “There was a really loud bang towards the left rear of the plane and a whoosh noise — and all the air masks dropped.

“They said there was a kid in that row who had his shirt was sucked off him and out of the plane and his mother was holding onto him to make sure he didn’t go with it.”

Another passenger, Jessica Montoia, said the experience was a “trip from hell”.

In a flight recording made by LiveATC.net, the pilot can be heard telling Portland air traffic controllers the plane had an emergency, was depressurised and needed to return to the airport.

Fleet grounded

Alaska Airlines CEO Ben Minicucci said the airline was taking the “precautionary step” of temporarily grounding its entire fleet of 65 Boeing 737-9 aircraft.

Each of the aircraft would be returned to service after full maintenance and safety inspections, which Minicucci said the airline anticipated completing within days.

The USA’s Federal Aviation Administration (FAA) later announced the worldwide temporary grounding of 171 Boeing 737 MAX 9 planes.

The flight was diverted about six minutes after taking off at 5.07pm on Friday local time, according to flight tracking data from the FlightAware website.

It landed at 5.26pm.

Source: X (Federal Aviation Administration)

The Boeing 737-9 MAX involved in the incident rolled off the assembly line and received its certification just two months ago, according to online FAA records.

The plane had been on 145 flights since entering commercial service on November 11, said FlightRadar24, another tracking service.

The flight from Portland was the aircraft’s third of the day.

Alaska Airlines has grounded its Boeing 737 MAX 9 fleet. Photo: Getty

Boeing said it was aware of the incident, working to gather more information and ready to support the investigation.

The Max is the newest version of Boeing’s venerable 737, a twin-engine, single-aisle plane frequently used on US domestic flights.

The plane went into service in May 2017.

Fatal crashes

Two Max 8 jets crashed in 2018 and 2019, killing 346 people and leading to an almost two-year worldwide grounding of all Max 8 and Max 9 planes.

The planes returned to service only after Boeing made changes to an automated flight control system implicated in the crashes.

Last year, the FAA told pilots to limit the use of an anti-ice system on the Max in dry conditions because of concern that inlets around the engines could overheat and break away, possibly striking the plane.

Max deliveries have been interrupted at times to fix manufacturing flaws.

The company told airlines in December to inspect the planes for a possible loose bolt in the rudder-control system.

The National Transportation Safety Board said in a post on X that it was investigating an event on the flight and would post updates when they were available.

-with AAP