Alaska Airlines flight 1276, a Boeing 737-900, taxis before takeoff from Portland International Airport in Portland, Ore., Saturday, Jan. 6, 2024. The FAA has ordered the temporary grounding of Boeing 737 MAX 9 aircraft after part of the fuselage blew out during a flight. (AP Photo/Craig Mitchelldyer)

PORTLAND, Ore. (AP) — Alaska Airlines again grounded all of its Boeing 737 Max 9 jetliners on Sunday after federal officials indicated further maintenance might be required to assure that another inflight blowout like the one that damaged one of its planes doesn’t happen again.

The airline had returned 18 of its 65 737 Max 9 aircraft to service Saturday following inspections that came less than 24 hours after a portion of one plane’s fuselage blew out three miles above (4.8 kilometers) above Oregon on Friday night. The depressurized plane, carrying 171 passengers and six crew members, returned safely to Portland International Airport with no serious injuries.

The airline said in a statement that the decision was made after receiving a notice from the Federal Aviation Administration that additional work might be needed. Other versions of the 737 are not affected.

“These aircraft have now also been pulled from service until details about possible additional maintenance work are confirmed with the FAA. We are in touch with the FAA to determine what, if any, further work is required before these aircraft are returned to service,” the airline said.

The FAA had ordered the grounding of some 737 Max 9s on Saturday until they could be inspected, a process that takes about four hours. The world’s airlines are currently operating about 171 737 Max 9s.

The aircraft make up about 20% of the Alaska Airlines’ fleet. As of midday, Alaska had canceled about a fifth of its Sunday flights, according to FlightAware.com. United Airlines, which also grounded its Max 9s, had about a 10% cancellation rate on Sunday.

Democratic Sen. Maria Cantwell of Washington state chairs the chamber’s Committee on Commerce, Science and Transportation and said she agreed with the decision to ground Alaska Air’s Max 9 jetliners for comprehensive inspections.

“Safety is paramount. Aviation production has to meet a gold standard, including quality control inspections and strong FAA oversight,” she said in a statement.

The National Transportation Safety Board is investigating Friday’s accident and is still looking for the door from the paneled-over exit that blew out.

Early Sunday afternoon, some local residents were scouring a patch of land with dense thickets, sandwiched between busy roads and a light rail train station. The area is located across from a sprawling hospital complex.

Adam Pirkle said he had ridden 14 miles, maneuvering his bicycle through the overgrowth, while searching. “I’ve been looking at the flight track, I was looking at the winds,” he said. “I’ve been trying to focus on wooded areas.”

Gavin Redshaw even brought his drone for an aerial view but hadn’t found anything either by Sunday afternoon. “Lots of trash, but no door,” he said.

There has not been a major crash involving a U.S. passenger carrier within the country since 2009 when a Colgan Air flight crashed near Buffalo, New York, killing all 49 people on board.

Flight 1282 took off from Portland at 5:07 p.m. Friday for a two-hour flight to Ontario, California. About six minutes later, the chunk of the fuselage blew out as the plane was at about 16,000 feet. One of the pilots declared an emergency and asked for clearance to descend to 10,000 feet, where the air would have enough oxygen to breathe safely.

Videos posted by passengers online showed a gaping hole where the paneled-over exit had been and passengers wearing masks. They applauded when the plane landed safely about 13 minutes after the blowout. Firefighters then came down the aisle, asking passengers to remain in their seats as they treated the injured.