An autopilot system which caused a plane to plunge 2900ft after it was struck by lightning should be changed, aviation experts have warned.

The Saab 2000 dived towards the sea at high speed after the strike near Shetland in December 2014.

Its pilot only regained control of the plunging plane after struggling with its autopilot, which he wrongly believed had turned itself off when the strike occurred.

The plane, which had 33 people aboard, fell to 1100ft before levelling-out and returning to Aberdeen.

The autopilot system had been countering the pilot's efforts to save the plane, pitching it downwards in an attempt to reach what it believed was the correct altitude, experts later found.

The Air Accidents Investigation Branch (AAIB) has now recommended the European Aviation Safety Agency (EASA) reviews the design of the Saab 2000's autopilot.

The AAIB said: "It is recommended that EASA review the design of the autopilot system and require modification to ensure that the autopilot does not create a potential hazard when the flight crew applies an override force to the flight controls."