A passenger plane sparked a massive mystery after it declared a mid-air emergency and then disappeared from tracking devices - before landing safely.

The Air Algerie Boeing 737-600 took off from Algiers this afternoon on a flight to Marseille but let out an emergency call shortly after take-off.

Flight tracking data showed the plane turning around and heading back towards the point where it took-off.

Before the plane arrived however, it disappeared from tracking systems sparking a mystery that lasted almost an hour.

Plane tracking site Flight Radar 24 listed the plane's status as "unknown" before revealing to its followers that it did not believe the plan had crashed.