737 Max Inspections Delayed as F.A.A. Orders Boeing to Revise Guidance

Federal regulators on Tuesday told Boeing to revise its instructions for how airlines should inspect its 737 Max 9, delaying the effort to get the jet back in the air after a part in one of the planes blew out during a flight late last week.

The Federal Aviation Administration said the company would revise the instructions it had released on Monday based on feedback from the agency, but it did not provide more details.

“Upon receiving the revised version of instructions from Boeing, the F.A.A. will conduct a thorough review,” the agency said in a statement. “The safety of the flying public, not speed, will determine the timeline for returning the Boeing 737-9 Max to service.”

The F.A.A. had said on Saturday that it would require inspections of the planes after a panel in one was blown out during an Alaska Airlines flight the previous day. Although no serious injuries were reported, the incident exposed passengers to powerful wind and raised fresh concerns about the safety practices at Boeing. The incident has also forced airlines operating the Max 9 to cancel scores of flights.

The blowout is the latest in a string of setbacks for Boeing, which has struggled to regain the public’s trust after two crashes involving the Boeing 737 Max 8 in 2018 and 2019 killed 346 people.

It was not immediately clear how Boeing’s initial plan fell short. The company said on Monday morning that it had shared instructions with airlines on how to inspect the affected panel, a plug where an exit door would otherwise be installed. Hours later, the F.A.A. said it had “approved a method to comply” with the agency’s Saturday order, appearing to confirm Boeing’s statement. The inspections are focused on the door plugs, door components and fasteners.

Alaska Airlines and United, the two biggest operators of the Max 9, said on Monday that they had found loose parts during preliminary inspections of the panel, also referred to as a door plug.

Investigators at the National Transportation Safety Board recovered the door plug, but they said on Monday that they were still searching for some related parts.

Boeing’s chief executive, Dave Calhoun, is expected to address employees at a meeting on Tuesday afternoon in the Seattle area where the company makes several of its planes, including the Max. Mr. Calhoun took charge of the company in January 2020 after his predecessor was forced out during the earlier Max crisis.

During Friday’s flight, carrying 171 passengers and six crew members, the plane’s crew struggled to communicate after the panel blew out. The pilots and flight attendants said they were surprised when the door separating the cockpit from the passenger cabin flew open, Jennifer Homendy, the chairwoman of the safety board, said during a news conference on Monday night. That subjected the pilots to the strong wind and cabin noise, making it hard for them to hear each other and communicate with air traffic control.

Ms. Homendy said that the cockpit door was designed to open during a rapid decompression event, but that the crew had not been made aware of that feature of the plane. Boeing, she said, planned to make changes to its manual to inform crews.

The incident could have been much more catastrophic if the plane had been at a higher altitude — the Alaska plane was at 16,000 feet when the panel blew out. If the plane had been cruising at more than 30,000 feet, passengers could have been moving about the cabin and would have had less time to safely put on oxygen masks and buckle themselves in.