The Federal Aviation Administration on Saturday ordered some Boeing 737 MAX 9 planes out of the air temporarily after a panel blew out during an Alaska Airlines flight Friday evening, prompting an emergency landing.

“The FAA will order the temporary grounding of certain Boeing 737 MAX 9 aircraft operated by U.S. airlines or in U.S. territory,” the agency posted on X Saturday. The grounding involves about 171 planes globally.

The FAA said its Emergency Airworthiness Directive “will require operators to inspect aircraft before further flight.” The required examinations take four to eight hours per aircraft, the order said.

The FAA’s order came less than 24 hours after a side panel on an Alaska Airlines MAX 9 blew off mid-flight, forcing the Ontario, California-bound plane to reverse course for an emergency landing in Portland.

One person was hospitalized, but no serious injuries were reported, reporter Debra Gil of KPTV-Portland posted on X.

Alaska Airlines grounded its MAX 9 fleet shortly after the incident on Friday. The airline returned some of the jets to service after inspections revealed no troubling issues, the Wall Street Journal reported.

Shortly before the FAA announcement, CNBC reported that United Airlines was grounding dozens of its MAX 9s, pending inspections. United and Alaska are among the biggest users of the jets, which are a bigger variant of the Boeing 737 MAX-8 that were involved in two fatal accidents that killed 346 people in 2019.

Alaska Airlines already returned some of the jets to service after inspections revealed no troubling issues, the Wall Street Journal reported.