While most reports of flying saucers are quickly dismissed by defence chiefs, the previously classified papers show the sighting, which took place near Pitlochry in 1990, was taken extremely seriously.
A former MoD official who investigated the case told Scotland on Sunday that despite strenuous efforts they could find no earthly explanation for the craft.
Witnesses reported seeing a large, diamond-shaped object hanging in the air next to a RAF Harrier above the A9 at Calvine, north of Pitlochry, on August 4, 1990.
The UFO is said to have hovered for about 10 minutes before zooming skywards at high speed and disappearing from view.
The apparent close encounter of the Caledonian kind was photographed by members of the public whose images appear to show a blurry, diamond-shaped craft next to a jet.
Fearing the pictures would spark significant media interest, the MoD decided to bring it to the attention of the Government.
A Whitehall official wrote in a memo: “Such stories are not normally drawn to the attention of ministers. “On this occasion, however, the MoD has been provided with six photographic negatives of an alleged UFO… and has been asked for comments almost certainly for inclusion in a forthcoming story.”
The memo suggested the media should be told that “no definite conclusion had been reached regarding the large diamond-shaped object”.
It has also emerged the MoD went on to commission a series of line drawings of the object the following year.
More info from old UFO Casebook article:
The photographs have been misplaced, lost, or hidden, and have never surfaced.
The MOD’s UFO Project had also been sent a number of intriguing photos and videos of UFOs, and had the means to have the images enhanced and analysed by various technical specialists.
Some intriguing images had arrived via the Scottish Daily Record in 1990, and a poster-sized photograph had been produced from one of the negatives and pinned to my (?) office wall by one of my predecessors.
The photograph had been taken in daylight and showed a vast, diamond-shaped UFO, metallic silver in colour, apparently hovering low over the Scottish countryside.
The photograph was removed in 1994 by the then head of the division, who had convinced himself that the picture showed a secret prototype aircraft codenamed Aurora — a hypersonic replacement for the SR-71 Blackbird that the US Government denied existed.
A question was asked in Parliament in 1996 about the location of this photograph, and the matter has subsequently been raised in a Freedom of Information Act request. Unfortunately, the photograph had disappeared, and could not be located.