US grounds some Boeing 737 Max planes after window blows out mid-air

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US federal regulators have temporarily grounded some Boeing 737 Max planes in American airspace after a section of an Alaska Airlines jet blew out in mid-air.

The emergency directive from the US Federal Aviation Administration affects about 171 jets worldwide. Carriers will need to inspect aircraft before further flight, a process that takes four to eight hours per plane, according to the directive.

“The FAA is requiring immediate inspections of certain Boeing 737 MAX 9 planes before they can return to flight,” FAA Administrator Mike Whitaker said. “Safety will continue to drive our decision-making as we assist the [National Transportation Safety Board’s] investigation into Alaska Airlines Flight 1282.”

The move is a blow to Boeing, which has struggled with manufacturing defects on the 737. It continues to experience the fallout from a 20-month worldwide grounding imposed by regulators after a pair of deadly crashes five months apart.

“Safety is our top priority,” Boeing said in a statement. “We agree with and fully support the FAA’s decision to require immediate inspections of 737-9 airplanes with the same configuration as the affected airplane.”

Alaska grounded 65 jets in its own fleet after an incident on a Friday night flight from Portland, Oregon, to California. It turned around 35 minutes into the journey and returned safely to Portland.

The plane, a 737 Max 9, was carrying 171 passengers and six crew. Photos and videos shared on social media by passengers showed a portion of a side wall and a window missing and oxygen masks deployed.

The aircraft reached an altitude of just over 16,000 feet during the flight, according to flight tracking data.  

Photos appeared to show a section of the fuselage, which is sometimes used as an optional exit door, torn away. Lower-cost airlines that carry more passengers often install the extra door to enable more evacuation options. The doors are permanently deactivated on Alaska Airlines aircraft. 

The FAA’s temporary grounding applies to all Max 9 aircraft with a mid-cabin door plug installed in the fuselage.

Spirit AeroSystems, a key Boeing supplier, installs the plugged door as part of its construction of the 737 Max fuselage, a company spokesman confirmed. The spokesman declined to comment further. Some of the Max fuselages Spirit delivered last year were found by Boeing to have improperly installed fittings on the vertical stabiliser, while another group had incorrectly drilled holes in the rear pressure bulkhead.

Britain’s Civil Aviation Authority said on Saturday that as there are no UK registered 737 Max-9 aircraft, “the impact on UK operated aircraft and consumers is minimal”.

The agency said it has written to all non-UK and foreign permit carriers to “ask for confirmation that inspections have been undertaken prior to any operation into UK airspace”.

Alaska said on Saturday that it had decided to take the “precautionary step” of temporarily grounding its fleet of Max 9s.

“Each aircraft will be returned to service only after completion of full maintenance and safety inspections,” said Ben Minicucci, the airline’s chief executive, in a statement. 

The airline said more than a quarter of the inspections were completed “with no concerning findings” and that it is working with Boeing and regulators to establish what happened.

United Airlines said it has “temporarily suspended service” on the jet. The airline already has inspected about 33 of its 79 Max 9s and expects to cancel about 60 flights on Saturday.

Boeing’s Max has been under scrutiny from regulators for several years after two models of the smaller variant, the Max 8, crashed in 2018 and 2019. The accidents killed a combined 346 people and caused regulators in one jurisdiction after another to ground the plane.

The FAA said the crew had reported a “pressurisation issue” and that it would investigate. Britain’s Civil Aviation Authority said it was “monitoring the situation” and was in contact with both Boeing and the FAA. 

Boeing said it was aware of the incident and was “working to gather more information”. It said a “technical team” was ready to support the investigation. 

The new Max 9 was delivered to Alaska Airlines in late October and certified in early November, according to online FAA data. The Max model is the newest version of Boeing’s 737 twin-engined aircraft and is often used on domestic US flights.

There are 215 Max 9 aircraft in service globally, according to data from aviation consultancy Cirium. Other big operators that use the model include United Airlines and Copa Airlines of Panama.

While the Max 9 accounted for roughly 20 per cent of Boeing’s 737 deliveries last year, it represents just 2 per cent of the manufacturer’s backlog, according to Jefferies analyst Sheila Kahyaoglu.