Airlines ground Boeing's 737 Max 9 after mid-air blowout

Rush of groundings triggered by US action marks most severe response since the entire fleet was parked in 2019

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The grounding of Boeing Co.'s 737 Max 9 quickly gathered pace, with carriers from the US to Panama to Turkey pulling the model from service for inspections after a fuselage section on a brand-new Alaska Airlines jet blew out during flight.

After Alaska Air kept its fleet of 65 737 Max 9s on the ground following the incident on 5 January, United Airlines Holdings Inc., the model's top operator, followed suit with some jets. Then the Federal Aviation Administration ordered a temporary grounding of 171 planes, accelerating the response among other airlines Aeromexico took all of its Max 9s out of service, and Panama's Copa Airlines did the same with most of its jets.

The cascading grounding marks the most severe response since Boeing's entire fleet of Max aircraft was parked in 2019 following two deadly crashes. The 737 Max is by far the company's most popular aircraft and its biggest source of revenue. The blowout puts the focus back on Boeing's manufacturing controls just as it was gearing up to raise output of its cash-cow model and turn the corner on past defects.

"We are very fortunate this didn't end up in something more tragic," Jennifer Homendy, the head of the National Transportation Safety Board, said at a press conference in Portland, Oregon, on Saturday.