An Air Algerie passenger jet travelling to Marseilles in understood to have declared an emergency in mid-air.
The Boeing 737-600 left Algiers this afternoon on a flight to Marseilles when it let out an emergency call.
Flight radar showed the plane turn around and head back towards the point where it took-off but before arriving.
The jet is thought to be returning to Algiers and flight radar shows the jet turning back on itself, heading over the Mediterranean and towards Mahon.
The plane is not currently on the radar - however aircraft do not show any activity under 17,000ft on this particular flight path, according to some experts.
