FAA temporarily grounds certain Boeing 737 MAX 9s after Alaska Airlines emergency landing

The Federal Aviation Administration is temporarily grounding certain Boeing 737 MAX 9 aircraft following a report of an "in-flight departure of a mid-cabin door plug" on an Alaska Airlines flight Friday.

The Alaska Airlines flight returned to Portland, Oregon, soon after takeoff after it "experienced an incident," prompting the airline to temporarily ground its Boeing 737-9 fleet, the airline said Friday.

Six crew members and 171 passengers were on board Flight 1282 bound for Ontario, California, the airline said.

The cabin became depressurized shortly after takeoff and the pilots asked for an emergency landing, according to the transcript of an air traffic control call from LiveATC.net. A photo posted on social media appeared to show a hole in the fuselage next to a passenger seat.

"The safety of our guests and employees is always our primary priority," Alaska said in a statement, "so while this type of occurrence is rare, our flight crew was trained and prepared to safely manage the situation."

CEO Ben Minicucci called the grounding "precautionary," saying in a statement the 65 planes will return to service "only after completion of full maintenance and safety inspections."

"We are working with Boeing and regulators to understand what occurred tonight, and will share updates as more information is available," Minicucci said.

The FAA said Saturday is it temporarily grounding certain Boeing 737 MAX 9 aircraft operated by U.S. airlines or in U.S. territory until they are inspected. The FAA says this will affect about 171 planes worldwide.

"The FAA is requiring immediate inspections of certain Boeing 737 MAX 9 planes before they can return to flight," FAA Administrator Mike Whitaker said in a statement. "Safety will continue to drive our decision-making as we assist the NTSB's investigation into Alaska Airlines Flight 1282."

The requirement was issued to "address the potential in-flight loss of a mid-cabin door plug, which could result in injury to passengers and crew, the door impacting the airplane, and/or loss of control of the airplane," the FAA's Emergency Airworthiness Directive states.

United Airlines said it is temporarily suspending service on certain Boeing 737 MAX 9 aircraft to conduct the FAA inspections. The airline said it has 79 of the planes in service, including 33 that have already received the inspections required by the FAA. The suspension is expected to cause about 60 cancellations on Saturday, United said.

United said Sunday that service on its Boeing 737 MAX 9 planes remains temporarily suspended as it conducts inspections required by the FAA. It continues to work with the federal agency to "clarify the inspection process and requirements" for returning the planes to service, United said in a statement.

"The FAA's first priority is keeping the flying public safe," the FAA said in an update Sunday. "We have grounded the affected airplanes, and they will remain grounded until the FAA is satisfied that they are safe."

Prior to the FAA order, Alaska Airlines said more than a quarter of inspections on its Boeing 737 MAX 9 fleet were complete as of Saturday morning with "no concerning findings."

Alaska said planes will continue to return to service as inspections are completed.

The airline has canceled 112 flights -- or 15% -- of its total flights on Saturday.

"We deeply apologize to our guests whose flights have been impacted," the airline said in a statement. "Guests whose travel has been impacted can go online to view flight options and rebook travel, place the value of their ticket in their Mileage Plan Wallet for future use, or request a refund." 

Some international airlines -- Turkish Airlines, Copa Airlines and Aeroméxico -- also temporarily suspended service on their 737 MAX 9s while doing inspections.

American Airlines and Southwest Airlines do not fly the Boeing 737 MAX 9.

The damage that led to the emergency landing appeared to be in the location of a "plug," said John J. Nance, an ABC News aviation analyst. Those are spots in the fuselage shaped similar to a door that aren't designed to open, even when the aircraft is on the ground. They could be converted to doors if the airline needs an extra boarding door.

The aircraft involved in the incident has been in service since October 2023, according to Federal Aviation Administration records. 

The National Transportation Safety Board said on Saturday they were sending a "go team" to Portland to investigate the incident.

The team will arrive on scene later Saturday and consists of experts in structures, operations and systems, the NTSB said.

Boeing said it has a technical team supporting the NTSB's investigation.

The aircraft maker also said it fully supports the FAA's decision "to require immediate inspections of 737-9 airplanes with the same configuration as the affected airplane."

"Safety is our top priority and we deeply regret the impact this event has had on our customers and their passengers," Boeing said in a statement.

ABC News' Clara McMichael and Sam Sweeney contributed to this report.