The US airline regulator has ordered the grounding of some Boeing 737 Max 9 jets after part of one plane fell off during an Alaska Airlines flight.

The Federal Aviation Administration (FAA) said the inspections would affect 171 plans.

On Friday the Alaska Airlines flight had to make an emergency landing after taking-off from the US state of Oregon.

United Airlines says it has carried out the inspections required by the FAA on some of its 79 Boeing 737 Max 9 planes.

Removing some of the aircraft from service is expected to cause about 60 cancellations on Saturday, the airline said in a statement.

Earlier, the FAA said it would "order the temporary grounding of certain Boeing 737 Max 9 aircraft operated by US airlines or in US territory."

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

The UK's Civil Aviation Authority (CAA) confirmed that there were no UK-registered 737 Max 9 aircraft.

"We have written to non-UK and foreign permit carriers to ask inspections have been undertaken prior to operation in UK airspace," they wrote on X, formerly Twitter.

In Friday's incident, the Alaska Airlines flight from Portland, Oregon to Ontario, California, had reached 16,000ft (4,876m) when it began its emergency descent, according to flight tracking data.

The airline, carrying 177 passengers and crew, landed safely back in Portland.

Images sent to news outlets showed the night sky visible through the gap in the fuselage, with insulation material and other debris also seen.

There were no immediate indications of the cause of the apparent structural failure, nor any reports of injuries.