AIR accident investigators have been unable to establish why a microlight plunged into the sea last year, killing the pilot and passenger.

Ray Hymas, 68, and Terry Driffield, 66, both members of Baxby Airsports Club at Husthwaite, near Thirsk, disappeared while flying back from the City of Derry Airport in Northern Ireland on June 9 last year, to Kirkbride aerodrome in Cumbria.

At the time of the crash, local pilots described the two men as experienced aviators who paid close attention to safety procedures.

A huge search operation ensued for the two people on board Ikarus microlight, involving sonar and seabed scanning.

Teams including coastguards, the RNLI, Northern Ireland Environment agency and North West Mountain Rescue took part in the operation.

Sections of tail had been spotted floating on the sea near Cushendun, Northern Ireland the day after the Ikarus disappeared, but no other evidence of what happened to the aircraft was found.

Now the Air Accident Investigation Branch (AAIB) has concluded its investigation into the crash and says due to the lack of material recovered, it is unable to say what happened that day.

The report concluded: “Analysis examination of images of the recovered pieces of the aircraft confirmed that it had stuck the sea with significant force.

“However, due to the limited amount of material recovered, and the lack of other substantive evidence relating to the accident, the AAIB was unable to determine the cause of the loss of this aircraft.”

On the day of the flight there had been fog and some low cloud in the area at the time and the pilot reported on his last radio contact he had descended to 1,200ft due to the conditions.

The alarm was raised by two other Yorkshire pilots who had taken off just before the Ikarus.

John Northage, of Burley in Wharfdale near Ilkley, and George Devlin, from Haxby, York, had planned to fly the same route around the coast of Northern Ireland and to the same destination, but they had not planned to fly in formation.

The pilot of that plane said that the last time he had seen the Ikarus, in the vicinity of Cushendun, he had “heard and saw nothing to indicate that there was a problem”.

The report added: “As he routed along the coast south of Cushendun, the visibility was approximately three to five km in haze with a poorly defined horizon, and there was fog over the sea.”