This strange flying object was seen by thousands and chased by jets. But after 5 years no one can explain it.
The evening skies over Belgium were crystal clear when the reports began to come in - first in their tens and then in their hundreds.
They spoke of a large triangular object, with bright lights at its three corners and center, floating low at a snails pace across the sky in uncanny silence.
It was the beginning of a mystery that has baffled scientists for five years - the best attested sighting of a UFO ever reported, and the one that refuses more stubbornly to yield to rational explanation.
For the object in the sky was tracked on radar and photographed by fighter pilots. It was sighted by no fewer than 13,500 people on the ground - 2,600 of whom, including judges and police, filed written statements describing in detail what they had seen.
And today the Sunday Express can reveal a confidential letter in which former Belgium Defence Minister Leo Delcroix admits that despite the most rigorous official investigation, no earthly explanation has been found.
The sightings are being treated with much seriousness this weekend that the EC is looking anew at plans to set up a UFO tracking center.
And the European Parliament has promised a full inquiry - amid strong calls for the British Ministry to be more open about its own investigations and findings.
As the reports began to come in on that March evening in 1990, military trackers a few miles south of Brussels picked up a large unidentified object on their radar. Two F-16 fighters were scrambled from Beauvechain, the nearest airbase, to intercept.
They climbed to 3,000 feet and locked on to the craft, reporting back to base that they had intercepted a "structured UFO". But then suddenly, according to the pilots, it began to behave in an extraordinary way.
Their on-board radar screens registered a quickly changing diamond shape, which suddenly accelerated to 600mph before slowing just as abruptly to 170mph. Then it plunged 3,300 feet in two seconds and accelerated from 170mph to 1,100mph in the same time. There was a marked absence of any sonic boom.
According to the instruments aboard the fighters, the craft pulled away at 46G - 46 times the force of gravity - enough to crush any human body to pulp. It headed west across the English Channel towards the fields of Kent before disappearing into the night sky.
During their 65 minute observation, the pilots took 15 photographs. But pursuit in their F-16s, capable of more than twice the speed of sound, was impossible.
Over the previous months, there had been sightings of a strikingly similar object in the skies over Belgium. And now there was hard scientific evidence to support them.
In his confidential letter, Mr. Delcroix admitted to the British writer Derek Sheffield, who has been investigating the "Belgium Wave" sightings, that there had been at least one earlier attempt by Belgium F-16s to intercept a similar UFO.
The Minister ruled out the possibility that what the witnesses had seen was a Stealth bomber, an AWACS or high-tech F-117 Stealth fighter. He could only conclude that there was no rational explanation of the evidence.
Last night a spokesman from the Belgium Ministry of Defense said: "These incidents were, and still are, being treated with the utmost seriousness. We gave chase but could not begin to keep up in the F-16s. Perhaps we will never fully fathom this mysterious business, but we continue to try."
In Britain, Admiral of the Fleet Lord Hill-Norton has lent his authority to the call for greater openness over investigations by the Ministry of Defense.
The former chairman of NATO's military committee has agreed to write a forward to Mr. Sheffield's forthcoming book on the sightings. A Deadly Concealment which is to be published in January.
In a letter to the 65 year old writer from Kent he said: "Let me say at once that I find the account of the two Belgium sightings entirely convincing.
"What is unusual is that the Belgium MoD, police, Air Force and politicians have been forthcoming."
Labour spokesman Dr David Clark told the Sunday Express last night that despite "solid information" from the Belgiums, the Ministery of Defense has persistently brushed the matter under the carpet.
"They have official recorded information and our view is the MoD is being far to secretive. They ought to be much more open on this issue. If it wasn't a UFO and was a Stealth bomber then we should be told."
Paul Beaver, who is a consultant for the highly respected Jane's Defense Weekly, said: "The sighting by the F-16s is certainly one of the best examples in Europe - fascinating and well documented."
Meanwhile Edward Ashpole, a distinguished scientist whose book The UFO Phenomena was published by Headline last week, said of the Belgium sightings: "The sheer volume of eye-witness accounts plus the radar tracking and the air force reports make it hard to ignore."
He said no American aircraft were present in Belgium airspace at the time of the sightings, and that no plane could hover or fly at only a few miles in an hour, as many of the listed witnesses claimed, without crashing.
Among eye-witness accounts, one of the most vivid comes from two sergeants in the Belgium gendarmerie. On November 29th, 1989, four months before the scrambling of the jets, Heinrich Nicoll and Hubert Von Montigny reported two triangular objects hovering at a very low altitude south of Brussels.
"It was twilight but still light enough to see," said Von Montigny. "Below one of the objects I saw three powerful search lights directed to the ground and one orange red flickering light."
The sighting lasted from 5.50PM until 8PM when the craft disapeared as mysteriously as it had arrived. They heard a "soft buzz" and were sure that what they saw was neither an aircraft nor a helicopter.
Ten other policemen also gave statements, as well as two judges and an engineer, an army colonel and air force meteorologist Valenzano Francesco.
On December 1st, 1989, Mr. Francesco was driving through the town of Ans, near Liege, just before 6pm. "My daughter was in the car with me," he said. "I looked up and I saw a flying object at a very low altitude of 100 to 150 meters."
"What attracted my attention was the blue and red lights around the object. When it was above us, we saw three big 'headlights' pointing downwards."
Army Lt Colonel Andre Amond sighted a UFO later that month. He was driving with his wife Chantal from his home to the station in Gembloux, a village near Brussels, at 6.45pm.
"In the sky to the right, just above the trees, I saw a series of three or four panels of lights, heading from north to south." he said.
"My wife demanded that I drive on, as the object seemed to be aggressive. There was no noise at all - the engine was silent. As I drove off, the big white light disappeared and was replaced by three white lights, which were less powerful."
"They formed a triangle, which was almost equilateral, and in its center of gravity was a larger red light."
"It seems strange, but despite the moonlight, it was impossible to make out the shape of the object itself, outside of this triangle of white lights."
To this day, nobody knows what it was that those and thousands of other witnesses saw. And five years on, in military archives all over the world, their evidence remains filed in the cabinet marked UFO.