An American passenger plane declared an emergency and performed a U-turn over Kent.

The United Airlines Boeing 767 plane, carrying 70 passengers and 11 crew, left Heathrow towards Newark Liberty International Airport, New York, at about 3.45pm today.

Video: A live stream captured the moment the flight touched back down at Heathrow

But it was highlighted red on the flight tracking site Flightradar, meaning the aircraft's transponder reported an emergency code.

The airline has said the warning was due to a potential mechanical issue.

A live stream captured the moment the flight touched back down at Heathrow.

United says it is working to get passengers on the next available flight.

A spokesman for the firm said: “United flight 147 returned to London Heathrow airport to address a potential mechanical issue.

“The flight landed safely and was subsequently cancelled.

“We are working to rebook customers on the next available flight to Newark.”

A spokesman for Heathrow confirmed the aircraft had landed safely and passengers were safely disembarked.

The plane travelled at 13,000ft over the Ashford area, and looped around Kent before returning to Heathrow.

In a post on X, Flightradar said: “Flight code UA147 is squawking 7700 and appears to be returning to London Heathrow.

“The aircraft involved is N665UA.

“It is a Boeing 767-300 built in July 1998 as MSN 29237.”

At one point, more than 10,000 people were following the plane’s journey on the site.

The Civil Aviation Authority could not comment.