RELATIVES of 14 men killed when a spy plane crashed in Afghanistan may have been shown a replacement aircraft after the one they were meant to see developed a fuel leak, an Oxford coroner said today.

The risk of leaks in the fuel tanks of RAF Nimrods has been highlighted during the inquest into the men's deaths.

When the hearing started last Tuesday, relatives were taken to RAF Brize Norton to view a Nimrod which was flown down from RAF Kinloss in Scotland.

But it emerged today that a possible fuel leak on the plane they were meant to see may have led to it being replaced.

Coroner Andrew Walker, ordering inquiries into the matter, asked lawyers at the Oxford inquest today: "Was the aircraft the family was shown last week the aircraft they were meant to see, or was another one flown down from RAF Kinloss because the other had a fuel leak?"

The men died when a 37-year-old Nimrod exploded just minutes after undergoing air-to-air refuelling near Kandahar on September 2, 2006.

The inquest has heard the explosion was caused by fuel leaking into a dry bay and igniting on contact with a hot air pipe.

The crew on Nimrod XV230 had no means of tackling the initial fire and so were forced to attempt an emergency descent to the Kandahar air base, but at 3,000ft the aircraft exploded into flames.

RAF Master Engineer Phil McConville, who was on the Tristar aircraft which refuelled XV230, said the procedure appeared to go to plan, with 10,000kg of fuel transferring successfully.

He said: "I believe in the two weeks we were out there it was only 230 that was flying so it was only 230 we were refuelling. I believe it was refuelled five or six times over the fortnight."

He said that after the tragedy it became a standard operating procedure for airborne planes receiving fuel to signal to the supplier craft to ease off the pressure when they were 90% full.

Flt Lt Scott Woodman, pilot of the Tristar, said he heard XV230's May Day call go out a few minutes after watching it fly out of view without any apparent problems.

"It did strike us that it could have been related (to the refuelling)," he said.

"We were questioning within ourselves whether everything was normal."

The 12 RAF personnel killed were Flight Lieutenant Steven Johnson, 38, from Elgin, Morayshire; Flt Lt Leigh Anthony Mitchelmore, 28, also from Elgin; Flt Lt Gareth Rodney Nicholas, 40, from Forres, Morayshire; Flt Lt Allan James Squires, 39, Nairn, Nairnshire; Flt Lt Steven Swarbrick, 28, from Inverness; Flight Sergeant Gary Wayne Andrews, 48, from Fochabers; Flt Sgt Stephen Beattie, 42, from Forres; Flt Sgt Gerard Martin Bell, 48, from Forres; Flt Sgt Adrian Davies, 49, from Forres; Sergeant Benjamin James Knight, 25, from Inverness; Sgt John Joseph Langton, 29, and from Forres; and Sgt Gary Paul Quilliam, 42, from Forres.

Lance Corporal Oliver Simon Dicketts, 27, of the Parachute Regiment, from Wadhurst, East Sussex; and Royal Marine Joseph David Windall, 22, from Hazlemere, Buckinghamshire, also died.