The pair, aged in their 20s, said they noticed a circular (half moon in their sketch) object high above the plane passing overhead. But the object descended rapidly beneath the mid section of the passenger plane and turned sharply to pass back above it and it then did a complete U-turn, appearing to wobble from side to side before fading out into the distance.

The brothers said that when they first saw the object it was a fairly bright silver colour but at other times it appeared a dull grey, depending how it caught the sun light during the incident on August 6 1995 at Trefnant, in the Vale of Clwyd.

Much later that day, at about 9.15pm, they again sighted what they thought was the same object. They reported that it was at the same altitude but that it was travelling much more slowly before disappearing behind clouds.

Two years earlier, January 17 1993, in the vicinity of the above incidents, several witnesses shared this following encounter experienced by one motorist in particular:

He was travelling along the A525 at night when he became aware of lights in a locality where there were none normally.

On getting closer he saw a pedestrian looking towards the lights and, as a car was behind the motorist, he continued to a junction turned around and headed back to the scene.

He was met by a self-lit helmet-shaped object approximately 30 metres from a farmhouse, hovering just above scrubland. He watched, along with other motorists who had also stopped, as lights on the object travelled along its surface.

Then, what appeared to be a search light, "scanned" the ground below. The witness, a trained nurse, did not speak to the other witnesses before leaving the scene confused and amazed at what he had seen.