Investigators say design defects are not suspected “at this time” in the Boeing MAX 9 | Boeing

U.S. aviation investigators were on the ground in Oregon on Sunday trying to figure out why a door panel on a new Boeing airliner exploded just minutes after takeoff, forcing the pilots to make an emergency landing with a hole “the size of a hole.” Refrigerator in the side of the plane.

The US planemaker was facing new scrutiny as regulators temporarily grounded a Boeing 737 Max 9 jet after part of a blocked exit door broke off on an Alaska Airlines plane at 16,000 feet (4,877 metres) over Portland, Oregon, on Friday with 171 passengers on board. And six people. Crew on board. The weeks-old plane has been modified to require fewer emergency exits because it has fewer seats.

But investigators – who have asked for the public's help in tracking down the door of the Alaska Airlines plane, which remained missing on Sunday – said preliminary findings do not indicate a widespread malfunction with the Boeing Max 9 plane.

“We'll look at the pressure system, we'll look at the door, the hinges,” Jennifer Homendy, chair of the National Transportation Safety Board (NTSB), said at a news conference. “Do we suspect that there is a general design issue with this aircraft based on previous incidents involving the Boeing Max? At this time no.”

Thousands of passengers, mostly in the United States, on Sunday faced flight cancellations expected to continue into next week, as airlines called in inspectors to comply with the Federal Aviation Administration (FAA) order.

No one was seriously injured during the emergency landing on Friday. However, this close call raised new safety concerns about Boeing aircraft, which occurred five years after two fatal accidents that killed 346 people and damaged the American company's reputation.

These fatal incidents occurred within a few months of each other in 2018 and 2019. Among them were the Boeing 737 MAX 8.

All Max planes were then grounded globally for about two years while the company's engineers worked to identify the problem — which turned out to be hardware malfunctions and poorly designed software that caused the planes to overtake pilots and fall out of the sky.

In December, Boeing asked airlines to inspect its 737 MAX planes For possible loose bolt In the rudder control system.

Friday's episode over Portland featured a different model. The 737 MAX 9 is now Boeing's largest single-aisle aircraft with a capacity of 220 seats. But most airlines have opted for fewer seats, meaning the plane's optional extra door is attached or covered.

It was part of the “extra” door encased in the fuselage – the main body of the plane housing the cabin, cockpit and cargo compartments – that exploded in midair.

Spirit AeroSystems of Wichita, Kansas, manufactured the fuselage. But Boeing has completed the complex, two-level assembly process at its factory outside Seattle, Washington.

Investigators are expected to examine both plants for potential defects in design, manufacturing and installation Quoted from sources to Reuters. “The assumption is that it was installed or equipped incorrectly,” one source said. Neither Boeing nor Spirit commented.

Door seals have been used to air condition aircraft and provide flexible seating across the industry for years.

The height at which the door panel exploded indicates a pressure problem, according to Jeff Guzzetti, a former NTSB and FAA official. “It happened at a lower altitude than I expected, which tells me the door wasn't doing its job of maintaining pressure inside the fuselage,” Guzzetti told NBC's Today show.

Passengers were shaken on Friday by the near-miss. Things couldn't have been worse because the explosion occurred before the plane reached cruising altitude, and the passengers were still seated with their leg belts fastened.

“Think about what happens when you're on a cruise. Everyone's up and walking, and people don't have seat belts,” Homendy said. “We could have ended up with something much more tragic.”

No one was sitting directly in the window seat next to the covered exit door. But there was a teenage boy and his mother in the middle and aisle seats. “The son's shirt was completely blown off and his whole body turned red, I think because of the irritation of the wind,” Elizabeth Lu, one of the passengers, told NBC.

Lu, 20, said she heard “Very loud bang,” I looked up and saw a large hole in the wall of the plane two rows away. Another passenger said the gap was “as is”. “Wide as a refrigerator”.

About 215 Boeing Max 9 aircraft are in operation globally, according to Cirium, an aviation data provider. Two US airlines – United and Alaska – account for 70% of the aircraft in service. Other operators include Panama's Copa Airlines, Aeromexico, Turkish Airlines, Flydubai and Icelandair.

The Federal Aviation Administration (FAA) halted and ordered inspections only of the 737 MAX 9, which was modified to reduce seating capacity and thus include a covered cabin exit door.

in statement Boeing said on Friday that safety is its top priority, and that its technical team supports the investigation by the National Transportation Safety Board. “We agree with and fully support the FAA’s decision to request immediate inspections of 737-9 aircraft in the same configuration as the affected aircraft,” she added.

According to the Aviation Safety Network. An unofficial database compiled from government sources indicates that more than 4,900 people have died in major accidents involving aircraft from the Boeing 737 family since their launch in the late 1960s.