Newly-released Ministry of Defence (MoD) files reveal a passenger jet approaching London had a near miss with an unidentified flying object.
The captain was so startled by the experience, he shouted "look out" to his co-pilot, after seeing a brown missile-shaped object shoot past overhead.
Despite investigations by the military and aviation authorities, no explanation could be found,
and the inquiry wound down, leaving the matter unsolved to this day.
The encounter was among a flurry of incidents in British airspace in the spring and summer of 1991, part of MoD documents charting supposed brushes with the unknown throughout the late 1980s and early 1990s which has been made available by the National Archives.
It is, however, the experience of the crew aboard an Alitalia flight that is the most intriguing. Having set off from Milan on 21 April, the airliner was over Lydd in Kent, coming in to land at Heathrow Airport. Flying at 22,000ft with 57 passengers on board, Achille Zaghetti, spotted the strange object some 1,000ft above him at about 8pm.
"At once I said, 'look out, look out,' to my co-pilot, who looked out and saw what I had seen," he recalled.
"As soon as the object crossed us I asked the ACC (area control centre] operator if he saw something on his screen and he answered 'I see an unknown target ten nm (nautical miles] behind you'."
Mr Zaghetti and his crew on the McDonnell Douglas MD80 aircraft were not the only people to catch sight of an unusual object in the skies above Kent that evening 17 years ago.
A Civil Aviation Authority (CAA) document notes that Southern TV broadcast a news item about a 14-year-old boy's reported sighting of a missile flying at low level, before it disappeared through the clouds.
Radar images showing the UFO were initially labelled "cruise missile??" but it was quickly established it was not a military weapon.
By 2 July, the MoD had concluded that the object had not come from the Army firing ranges in the Lydd area and that there was no known "space-related activity" that night.
An unnamed Whitehall mandarin wrote of the incident: "It is our intention to treat this sighting like that of any other unidentified flying object and therefore we will not be undertaking further investigation."
Less than two months later, another sighting came in the south-east of England, when on 17 June, four passengers on board a Dan Air Boeing 737 reported seeing a "wingless projectile" pass beneath their aircraft, which was ascending from Gatwick Airport, bound for Hamburg.
Air traffic control at Gatwick saidthat it was "unaware of anything unusual occurring at that time".
On 15 July, the pilot of a Britannia Airways 737 reported seeing a "small black lozenge-shaped object" travelling at speed on the approach to Gatwick.
An investigation found that the object "did not seem to fit any recognisable piece of aviation equipment" and failed to reach a firm conclusion.
Handout image issued by the National Archives of an incident report detailing the moments when an Alitalia passenger jet coming in to land at Heathrow Airport had a near miss with a UFO.
Dr David Clarke, a UFO expert and journalism lecturer at Sheffield Hallam University, said such documents would shed new light on relatively little-known sightings.
NOW THEY'RE OUT THERE
A FORMER US Air Force fighter pilot was convinced he encountered a spaceship over the skies of Britain in the 1950s.
Newly released Ministry of Defence files reveal Milton Torres was told to intercept a UFO with "very unusual flight patterns" over East Anglia, before it suddenly disappeared.
The files also reveal the MoD tried to stop military helicopter crews photographing crop circles for fear it contradicted the official line that it had no interest in the phenomenon.
They also publish for the first time eccentric letters from people who claim to be from alien races. The correspondence includes one woman's claim that her spaceship came down in Britain during the Second World War and was recovered by the military.
The full article contains 672 words and appears in The Scotsman newspaper.
