A SQUADRON of US fighter jets were a second away from colliding with a coastguard search a rescue helicopter in a near-miss incident over the Cairngorms.

Details of the incident, which took place on March 3, have only just emerged.

A report by the Uk's Airprox Board concluded that there had been "a risk of collision" when three F15s flew within 3000ft of the civilian aircraft during a training exercise over Glen Feshie in the Highlands.

The high-speed fighter jets are able to close the distance - equivalent to just over half a land mile - within a second, but none of their pilots realised the Sikorsky S-92 helicopter was even in their airspace.

It was involved with a search and rescue operation in the area at the time.

The UK Airprox Board, which investigates near misses in British airspace, said the safety of the aircraft was at risk.

In a report published yesterday, the panel concluded: "Some members had the view that at [3000ft] the separation might not be considered unduly close and that there had been no risk of collision.

"Others felt that the overtake speed of the F15 formation, along with the lack of any visual sighting, had resulted in a collision being avoided only through providence.

"Ultimately, after a protracted debate, the majority of members agreed that there had been a risk of collision and that safety margins had been much reduced below the norm."

The fighter jet pilots only discovered later how close they had come to a potentially catastrophic mid-air crash.

The area over the Cairngorms had been assigned as a “temporary danger area” during the coastguard helicopter's rescue operation.

However, the investigation found that the fighter pilots had planned their flight-path prior to the temporary danger area being put in place, and did not have details of it on their charts.

The pilot of the helicopter reported that he first spotted a first jet in the 12 o’clock position, flying at the same altitude and just under two miles away.

The helicopter crew then witnessed another three jets much closer, at just over 3,000ft to the right hand side of their aircraft, and also flying at the same altitude.

The aircraft had approached from directly behind the helicopter and were subsequently identified as F-15s.

The helicopter pilot then made a call which was answered by the F-15 formation leader to explain that they had flown through the temporary danger area.

The risk of collision was assessed as low by the helicopter pilot.

The F-15 leader reported that his formation was conducting a low-flying exercise in the area. He told investigators at Airprox that he subsequently instructed the jets to climb out of the danger area to a safer 7000ft.

The pilot had also assessed the risk of any collision as low.

Following the incident, the US Air Force has implemented new procedures to ensure that flights are updated of potential conflicts.