Investigators say finding the door plug is key to determining why the accident occurred.
ADVERTISEMENTA piece of the fuselage that blew off an Alaska Airlines flight on Friday has been found in the backyard of a person living in a suburb of Portland in the United States.
The door plug tore off the Boeing 737 Max 9 shortly after it had taken off from Portland en route to Ontario in California, depressurising the plane and forcing the pilots to make an emergency landing.
Authorities said it was fortunate that the piece of fuselage had fallen out while the plane was at 16,000 feet and the 171 passengers on board were still required to be wearing seatbelts.
The National Transportation Safety Board (NTSB) said finding the part was key to determining why the accident had occurred.
On Saturday, the US Federal Aviation Administration (FAA) ordered the temporary grounding of 171 Boeing Max 9 jets installed with the same panel, which covers an optional exit door mainly used by low-cost airlines.
The incident happened after Alaska Airlines pilots reported pressurisation warning lights on three earlier flights of the same jet model in December and early January.
But the NTSB said investigators said it was not clear yet if there was any connection between this and the rapid depressurisation incident on Friday.
Thousands of passengers were left stranded after hundreds of flights were cancelled over the weekend by United Airlines and Alaska Airlines.
Boeing has delivered 218 Max 9s worldwide, but not all of them are covered by the FAA order.
In 2019, global authorities subjected all Max planes to a wider grounding that lasted 20 months after two Max 8 jets crashed, killing 346 people.