The riddle of the lost flight

In 1975, a tiny aircraft took off from Mull, never to be seen again. Has the discovery of a wreck on the seabed solved a 30-year mystery? Tim Luckhurst investigates

A chance discovery by Royal Navy warships may prove to be the key that can unravel a 29-year-old mystery involving a veteran wartime pilot who was found dead, but uninjured, four months after his aircraft went missing. The story of the pilot, whose body was discoveredon a remote Scottish island hillside in April 1976, has fascinated aviation experts and conspiracy theorists for nearly three decades. How did he become separated from his aircraft? Why was his body not located by the search teams that scoured Mull in the immediate aftermath of his disappearance? Was he really at the wheel of the tiny Cessna in which eyewitnesses insist he took off on Christmas Eve 1975?

In the course of a coastal mapping operation early this month the minesweepers HMS Pembroke, HMS Penzance and HMS Inverness located a mystery aircraft 30 metres beneath the surface in the waters off Oban, on the west coast of Scotland. Pembroke deployed a remote underwater camera to take pictures of the wreckage. The images show a small aircraft, with one wing still attached. Speculation is growing that the plane may be the Cessna.

The plane that went missing that night was a red-and-white Cessna F150H, registration mark G-AVTN. In September 1975 it was purchased by Ian Hamilton, who kept it at the North Connel airport near Oban. But Hamilton was not the pilot when G-AVTN went missing on Wednesday 24 December 1975. At the controls was a 55-year-old businessman from London, Norman Peter Gibbs, who had learnt to fly as a serviceman during the Second World War. Gibbs's body was found, in April 1975, on Mull by a local shepherd, Donald MacKinnon. It was lying on a hillside about a mile from the tiny grass airstrip from which Gibbs had taken off. No wreckage was found to indicate the fate of the aircraft.

The facts, assembled in the book Scottish Mysteries by Donald M Fraser, are undisputed. Gibbs arrived on Mull on Saturday 20 December along with his girlfriend, Felicity Grainger, a 32-year-old university lecturer. Gibbs, the managing director of a property-development company called Gibbs and Rae, was looking for investment opportunities. He was interested in buying a hotel. Gibbs found out that a Cessna aircraft was available to hire from the manager of the Glen Forsa Hotel. He had a private pilot's licence, and about 2,000 hours of flying experience.

On Christmas Eve, Gibbs and Grainger flew the plane from Mull to Broadford on the Isle of Skye, and spent the day inspecting property. They flew back to Mull in time for dinner. Having eaten and enjoyed modest quantities of whisky and red wine, Gibbs outlined his theory that it might be possible to make night landings at Glen Forsa, although the little airstrip was not equipped with runway lights. Gibbs believed an air link would be precious in making a luxury hotel development profitable.

He decided to take the Cessna up and land it in the dark. If Gibbs had not been such a confident and ostensibly experienced pilot, others might have told him that what he was planning was illegal as well as dangerous. But he seemed sublimely confident. He had borrowed two powerful torches to use as makeshift landing lights. Felicity would remain on the ground and use them to guide him in.

The couple arrived at the airstrip at about 9.30pm. Gibbs taxied the Cessna to the eastern end of the runway. Here, Grainger got out and followed her boyfriend's instructions to place the two torches about a foot apart facing the aircraft. He seemed content that, in the clear sky, the torch beams would give him an adequate reference point at which to aim.

Gibbs roared into the sky. He had told Grainger that he would land once, just to prove that it was straightforward, and then return. The Cessna failed to return. A 10pm she returned to the hotel. Two hours after Gibbs had taken off, the police were called in. The weather had deteriorated dramatically but, in freezing rain and snow, Mull's tiny police force did their best to cover the flight path along which they believed the Cessna had flown.

They found nothing. Nor did the RAF and Naval Air Service helicopters which, on Christmas Day, began scouring the island and deployed sonar equipment to look for wreckage. The search continued for days, using hundreds of volunteers. Neither Peter Gibbs nor his aircraft were located. Pilot and Cessna seemed to have disappeared without trace.

When, four months later, Donald MacKinnon stumbled across Gibbs's body, the circumstances were ideal for the emergence of conspiracy theories. Why had the body not been located by the searchers? Why was there no trace of the aircraft in which Gibbs had taken off? Had it really been Gibbs at the controls that night? Speculation also mounted about the presence of a mystery character on the runway before Gibbs took off. Had Gibbs planned his disappearance to escape business debts?

The fatal-accident inquiry into Gibbs's death did little to quell the tide of rumours. Gibbs's body was uninjured, apart from a small abrasion on the left leg. It did not look like the corpse of a man who had crashed an aircraft into a hillside. Had he crashed at sea, and somehow struggled ashore and died there of exposure? Neither Gibbs's body nor his clothes revealed evidence that they had been immersed in salt water. But the inquiry considered it likely that four months of rain, wind and snow might have washed sea salt away.

The finding of the inquiry was that Gibbs had died of exposure, not as a result of injuries consistent with an air crash. He had, somehow, become separated from the Cessna. As the procurator fiscal Graeme Pagan concluded, "This inquiry has taken some mystery out, but until the plane is found, then the mystery will remain."

In September 1986 two clam fishermen from Mull were diving in the Sound of Mull when they reported coming across a red-and-white aircraft on the seabed. From what they were able to see, they did not detect any human remains in the plane. The divers, who were brothers called Richard and John Grieve, confirmed that the plane they saw was a Cessna, and that it did bear the registration G-AVTN. Their report was considered credible. It seemed that Gibbs, lost in the dark, had descended low over the sea while desperately trying to locate the airstrip. Somehow, fully clothed and in near-freezing conditions, he had managed to swim more than half a kilometre to the shore and had then climbed the hillside, only to die of exposure.

It is the most likely answer. But the wreckage found by the Grieve brothers was never recovered. And the pictures taken were not good enough to allow expert air-accident inspectors to assess whether the crash had been survivable. The plane that the brothers found appeared to be seriously damaged. The engine had been detached from the airframe, and was lying some distance from it. One of the wheels appeared to have been torn off. They reported that both wings were missing.

The aircraft sighted by the Royal Navy appears to be in the same spot. But there are discrepancies. Navy divers and the film taken by HMS Pembroke suggest that one wing is still firmly attached to the fuselage. A Royal Navy spokesman, Neil Smith, said: "We think it could be a Cessna, but we have not confirmed that yet."

A possibility exists that this is not Peter Gibbs's plane at all. A six-seater Piper Aztec is known to have ditched in the area 20 years ago. Its crew escaped unharmed. If what the navy has found is Cessna G-AVTN, then it may only be a matter of time before the mystery of Peter Gibbs's last flight is finally unravelled.