The US National Transportation Safety Board said the "key missing component" from the Boeing 737 MAX 9 jet involved in an Alaska Airlines emergency landing had been recovered from the backyard of a suburban home, Report informs referring to Reuters.

The plug door tore off the left side of an Alaska Airlines jet on Friday following takeoff from Portland, Oregon, en route to Ontario, California, depressurizing the plane and forcing pilots to turn back and land safely with all 171 passengers and six crew on board.

The Federal Aviation Administration (FAA) ordered the temporary grounding of 171 Boeing MAX 9 jets installed with the same panel, which weighs about 60 pounds (27 kg) and covers an optional exit door mainly used by low-cost airlines.

The missing plug door was recovered on Sunday by a Portland school teacher identified only as "Bob" in the Cedar Hills neighborhood who found it in his backyard, NTSB Chair Jennifer Homendy said, saying she was "very relieved" it had been found.