The US airline regulator has ordered the grounding of some Boeing 737 Max 9 jets.

This, after a part of one plane fell off during an Alaska Airlines flight.

According to BBC News, the Federal Aviation Administration (FAA) said the inspections would affect 171 planes.

Required inspections will take around four to eight hours per aircraft.

In Friday’s incident, the Alaska Airlines flight from Portland, Oregon to Ontario, California, had reached 16,000ft when it began its emergency descent.

The plane landed safely back in Portland – There were no immediate indications of the cause of the apparent structural failure, or any reports of injuries.