For Alaska Airlines and its passengers, a return to normal may take a while.
The carrier has grounded a fifth of its fleet after a fuselage panel blew out on one of its Boeing 737 Max 9 jets on Friday night, leaving a hole in the side of the plane.
The airline announced Wednesday that it would keep its Max 9 jets grounded until at least Saturday while it awaited instructions from Boeing on how to carry out safety inspections.
United Airlines, with 79 planes, and Alaska, with 65, are the heaviest users of the Max 9 in the United States. But the jet model makes up less than 10 percent of United’s fleet, allowing it to fill in gaps on planned routes more easily than Alaska.
Grounding the Max 9 has forced Alaska to cancel as many as 150 flights per day. About 20 percent of its flights were canceled on Wednesday, according to FlightAware, which tracks flight data.
“It’s been extremely disruptive,” said Bret Peyton, a director of operations at Alaska Airlines.
It’s unclear when those jets will be back in the air.
The day after the incident, the Federal Aviation Administration ordered all 171 Max 9 jets in the United States to be grounded and inspected. Boeing gave airlines instructions on how to inspect the jets, but the aviation agency said Tuesday that those instructions needed to be revised.
Though it’s unclear how Boeing’s initial inspection instructions fell short, the F.A.A. said the “safety of the flying public, not speed,” would take priority in returning the planes to service.
“It’s a waiting game on the F.A.A.,” said Kathleen Bangs, an aviation specialist at FlightAware. “You can be sure those airlines, especially Alaska, are in close contact with them.”
The National Transportation Safety Board is investigating the manufacturing and installation of the panel, known as a door plug, that flew off. Alaska and United said they had found loose parts during preliminary inspections of the panels.
As Alaska grounded the Max 9, it looked at whether other aircraft, even if a different size, could complete the same routes. For instance, if a flight was going somewhere with difficult weather and was at risk of being canceled anyway, canceling it early could free up the plane.
“It’s a really complex set of considerations we take,” Mr. Peyton said.
Ms. Bangs said various jet models could be used interchangeably on routes over land, so specific routes wouldn’t necessarily be disproportionately affected by the grounding.
She noted that Alaska, whose primary hub is Seattle-Tacoma International Airport, might also be facing additional delays related to a winter storm in the Pacific Northwest.
Transportation Secretary Pete Buttigieg told reporters in Washington on Wednesday that the chief executives at Alaska and United had “confirmed their commitment to take care of passengers” whose flights were canceled as part of the Max 9 grounding.
Mr. Buttigieg noted that unlike a weather-related cancellation, this situation should be considered a “controllable” one, meaning customers are entitled to compensation.
January is typically a slow time for airlines. Had the interruption happened weeks earlier during the holiday season, “it would have been a disaster,” said Helane Becker, an airline analyst at TD Cowen.
“It’s unfortunate that it happened, but the fact that it happened now is better than had it happened during a busier time,” Ms. Becker said.
Mark Walker and Niraj Chokshi contributed reporting.