F.A.A. Orders Airlines to Ground Some Boeing 737 Max 9 Jets After Midair ‘Incident’

The Federal Aviation Administration on Saturday ordered U.S. airlines to stop using some Boeing 737 Max 9 planes until they are inspected, less than a day after one of those planes lost a chunk of its body in midair “with an extremely loud pop,” terrifying passengers before the jet safely returned to ground.

Those on board Alaska Airlines Flight 1282 described an unnerving experience during the 20 minutes of the flight, which was destined for Ontario, Calif., but returned to Portland International Airport in Oregon on Friday night. As yellow oxygen masks dangled above their heads, a powerful wind tore through a gaping hole that showed the night sky and the city lights below. No one aboard the plane was seriously injured.

A passenger, Vi Nguyen of Portland, said that she woke up to a loud sound during the flight. Then she saw a large hole in the side of the aircraft.

“I open up my eyes and the first thing I see is the oxygen mask right in front of me,” Ms. Nguyen, 22, said. “And I look to the left and the wall on the side of the plane is gone.”

“The first thing I thought was, ‘I’m going to die,’” she added.

The F.A.A.’s order will affect about 171 planes.

While the F.A.A. has yet to publicly discuss the cause of the incident, in its grounding order to the airlines, it asked that they inspect what it called a “mid cabin door plug.” Some of the Boeing 737 Max 9s are configured with fewer seats and, therefore, do not need all the emergency exits originally designed for the plane. The unneeded exits are filled with a plug.

Alaska Airlines confirmed in a statement on Saturday afternoon that it had started inspecting the door plugs and cleared 18 of its 65 Max 9s to return to service. The airline said it expected to complete the inspections in the next few days.

Forrest Gossett, a spokesman for Spirit AeroSystems, said on Saturday that his company installed door plugs on the Max 9s and that Spirit had installed the plug on the Alaska Air flight.

United Airlines has 79 Max 9s in service, more than any other airline, according to Cirium, an aviation data provider. Alaska’s 65 represent about a fifth of its fleet.

“Safety will continue to drive our decision-making,” the agency’s administrator, Mike Whitaker, said in a statement. The F.A.A. is working with the National Transportation Safety Board, which is leading an investigation into the Alaska flight.

United Airlines said on Saturday that it would be suspending the use of certain Boeing 737 Max 9s it operates as a result of the F.A.A.’s order. Of the airline’s 79 Max 9s in service, 33 have already been inspected, the airline said in a statement. The airline said the removal of the planes from service was expected to be the cause of about 60 cancellations on Saturday.

“We are working directly with impacted customers to find them alternative travel options,” the airline said in statement.

The F.A.A. said that the required inspections should take four to eight hours per plane to complete.

Boeing issued a statement shortly after the F.A.A.’s grounding order. “Safety is our top priority and we deeply regret the impact this event has had on our customers and their passengers,” Jessica Kowal, a spokeswoman for Boeing, said in the statement. “We agree with and fully support the F.A.A.’s decision to require immediate inspections of 737-9 airplanes with the same configuration as the affected airplane.”

Boeing’s Max aircraft have a troubled history. After two crashes of Max 8 jets killed hundreds of people within several months in 2018 and 2019, the Max was grounded around the world.

Alaska Airlines Flight 1282 departed for Ontario International Airport at 5:07 p.m. and was diverted back to Portland six minutes later, according to FlightAware, a flight tracking website. It reached a maximum altitude of about 16,000 feet, when its speed was recorded at more than 440 miles per hour, and landed in Portland at 5:27 p.m.

The cause of the midair problem was not immediately clear. Keith Tonkin, the managing director of Aviation Projects, an aviation consulting company in Brisbane, Australia, said that an excessive difference in the air pressure inside versus outside the cabin could have caused the wall to break off.

Passengers were probably able to breathe normally even when the plane was at its highest altitude, Mr. Tonkin added.

A friend of Ms. Nguyen, Elizabeth Le, 20, said she heard “an extremely loud pop.” When she looked up, she saw a large hole on the wall of the plane about two or three rows away, she said.

Ms. Le said no one was sitting in the window seat next to the missing fuselage, but that a teenage boy and his mother were sitting in the middle and aisle seats. Flight attendants helped them move to the other side of the plane a few minutes later, she said. The boy appeared to have lost his shirt, and his skin looked red and irritated, she added.

“It was honestly horrifying,” she said. “I almost broke down, but I realized I needed to remain calm.”

There were announcements over the speaker system, but none were audible because the wind whipping through the plane was so loud, she said. After the plane landed, paramedics came on board to ask whether anyone was injured, she added. A man seated in the row immediately behind the hole said that he had hurt his foot.

Ms. Le said the passengers were not given an explanation of what had happened. In a video she took of the flight, passengers can be heard clapping after landing. “Oh my god,” someone says.

After landing, Ms. Le said that she and her friends were boarding another flight to Ontario later that night.

Evan Smith, 72, a lawyer who was returning to his home in Murrieta, Calif., after visiting his daughter and son-in-law in Portland, said he heard a loud “bang” and saw some “dusky, smoky stuff” swirling around the cabin.

Mr. Smith said his experience as a military police officer taught him that it was important to keep a cool head. Plus, he said: “The plane was stable. It wasn’t shaking. It wasn’t making any weird maneuvers. It was just flying steady.”

He added, “I was sure the aircraft was fine and we were going to get down OK.”

The plane was new, having been certified in November, according to the F.A.A. registry of aircraft. It entered commercial service that month and has since logged 145 flights, according to Flightradar24, another flight tracking site.

Sara Nelson, the president of the Association of Flight Attendants, a union that represents flight attendants at Alaska, United and other airlines, said in a statement on Saturday that she welcomed the inspections required by the F.A.A.

“This is a critical move to ensure the safety of all crew and passengers, as well as confidence in aviation safety,” she said. “Lives must come first always.”

As of midday on Saturday, Alaska Airlines had canceled about 100 flights, or 13 percent of those scheduled for the day, according to FlightAware, a flight tracking website. Dozens more flights were delayed.

Passengers were swarming Alaska Airlines’ phone lines on Saturday to rebook canceled flights and determine whether upcoming flights would be affected by the grounding. Customer service hold times, passengers were saying on social media, exceeded seven hours.

In 2018, Lion Air Flight 610, a 737 Max 8, crashed into the ocean off the coast of Indonesia, killing all 189 passengers and crew members. Less than five months later in 2019, Ethiopian Airlines Flight 302 crashed shortly after leaving Ethiopia’s capital, Addis Ababa, killing all 157 people on board.

The Max planes were grounded after the second crash. Boeing made changes to the plane, including to the flight control system behind the crashes, and the F.A.A. cleared it to fly again in late 2020. In 2021, the company agreed to a $2.5 billion settlement with the Justice Department, resolving a criminal charge that Boeing conspired to defraud the agency.

In December, Boeing urged airlines to inspect all 737 Max airplanes for a possible loose bolt in the rudder-control system after an international airline discovered a bolt with a missing nut during routine maintenance. Alaska Airlines said at the time that it expected to complete inspections for its fleet in the first half of January.

The Max planes are in wide use. Of the nearly 2.9 million flights scheduled globally in January, 4.3 percent are planned to be carried out using Max 8 planes, while 0.7 percent are slated to use the Max 9.

The Max is the most popular plane in Boeing’s history, accounting for a fifth of all orders placed since 1955, according to company data.

Rebecca Carballo contributed reporting.