US Air Force plane declares mid-air emergency over UK

It's the most tracked plane in the world

The US Air Force Boeing C-17A Globemaster III is operating a flight from Portsmouth, USA, to an unknown destination, having already been flying for multiple hours.

The plane squawked 7700, meaning to declare a mid-air emergency, over the west coast of Scotland, south of Glasgow.

The plane has since diverted from its original heading, turning north and starting a loop over Newcastleton.

It is fairly common for planes to squawk 7700, with it happening multiple times around the world each day.

It is not known yet the reason for declaring a mid-air emergency, although these kind of incident are fairly common and could be anything from a technical issue to a sick crew member.

The plane is currently the most tracked in the world on Flightradar24.

You can follow it live here.