A US military plane has declared a mid-air emergency just minutes after taking off from a Scots airport.

The McDonnell Douglas KC-10A Extender, with callsign ROMA91, took off from Prestwick Airport in Ayrshire at around 10.06am on Thursday.

It declared a Squawk 7700 emergency at around 10.12am.

The Herald: FlightRadar.comFlightRadar.com

It is not yet known what sparked the emergency call, however a Squawk 7700 is used to identify an aircraft that has a possible issue and enables it to have priority over other air traffic. 

The plane, which is operated by the US Air Force, made the U-turn while travelling over the Firth of Clyde.

FlightRadar maps show the aircraft having circled several times before heading back to land at Prestwick.

The Herald:

This is the third of such incident to be recorded in recent days.

We previously told how an Eastern Airways flight, operating on the Aberdeen to Sumburgh route, declared the emergency on Tuesday morning.

And on Thursday a cargo plane from Charles De Gaulle Airport in France had to turn back while en route to Edinburgh after the crew experienced an issue with a door.

The Herald has approached the US Air Force for comment.

This is a breaking story and will be updated.