At first, the witnesses claimed, all you noticed were the lights.

They were so bright you could read by them, so brilliant that a policeman described them as "like lights on a huge football field." Only gradually did you notice the object they emitted from — a hulking triangular shape, with three enormous spotlights pointed toward the ground, and a red, flashing light at its center. "The whole thing," recalled the policeman, as if barely able to believe it himself, "was floating in the air."

It was a clear November night in 1989, near the town of Eupen, Belgium, which sits some seven miles from the German border. Heinrich Nicoll, the policeman, and his partner, Hubert Von Montigny, called their dispatcher to report the object they'd stumbled on while on a routine patrol. "Suddenly, they told me they were seeing a strange object in the sky," Albert Creutz, who was on the receiving end, told Unsolved Mysteries in a 1992 episode. "It made no noise. We joked about it and said it might be Santa Claus trying to land."

But by the time the evening was over, at least 30 different groups and three separate pairs of police officers would allege to have seen the unidentified flying object. And they wouldn't be the last. Belgium's months-long "UFO wave" culminated 30 years ago today — on March 30, 1990 — in a physics-defying chase through the skies over Europe as two Belgian Air Force F-16s pursued mysterious objects on their radars that they couldn't even see.

But, okay okay, did aliens really visit Belgium? It certainly seems deeply, deeply unlikely. Yet three decades later, it's still hard to entirely dismiss the 2,000-odd sightings that took place in the country between November 1989 and April 1990. As Patrick Ferryn, the president of the Belgian committee for the study of space phenomena, SOBEPS, told The Telegraph, "You must know that most of these sightings will have the most banal explanation but there is a residue, which we simply can't explain. And of those, there may be two or three where we may have questions over where they came from."

Lots can be ruled out, though. For example, a classic photograph of the triangle-shaped aircraft, known as the "Petit-Rechain picture," is without a doubt a hoax — the forger admitted as much when he came forward in 2011. "We made the model with polystyrene, we painted it, and then we started sticking things to it, then we suspended it in the air ... then we took the photo," the prankster confessed to Reuters. Brian Dunning, the writer and producer of the podcast Skeptoid, also refutes a number of the sightings, arguing that the November apparitions were in fact a helicopter, and that the police officers were interviewed by a biased ufologist. Conflicting information, published by Reuters, claims instead that the lights over Eupen were from "a Soviet satellite breaking up."

Regardless, where things really start to get strange is in March 1990. At that point, there had been months of sporadic sightings throughout Belgium, including by an army colonel, André Amond, who claimed to have seen the lights while driving in his car with his wife in December. The Belgian military, needless to say, was well aware of the descriptions pouring in from across the country, and it had little in the way of answers.

Then-Chief of Operations of the Air Staff, General Wilfried De Brouwer — who offered his account to investigative reporter Leslie Kean for her 2010 book UFOs: Generals, Pilots, and Government Officials Go on the Record — said that his initial belief was that the American military must have been testing some sort of experimental aircraft over his country. He went as far as to file inquiries with the U.S. Embassy in Brussels, prompting the Americans to create a memo, dryly titled "Belgium and the UFO Issue," which confirmed that "no USAF stealth aircrafts were operating in the... area during the periods in question."

The reports were credible enough, though, that Belgium's Air Force, federal aviation authorities, and police devised a plan to try to catch one of the unidentified intruders in action by preparing F-16s to quickly take off if a sighting was ever reported by both the police and a radar station at the same time. Sure enough, as De Brouwer recounts in UFOs, that night came on March 30, when "several policemen" and "two military radar stations" spotted an unknown object. "Once aloft, the [Belgian] pilots tried to intercept the alleged crafts, and at one point recorded targets on their radar with unusual behavior, such as jumping huge distances in seconds and accelerating beyond human capacity," De Brouwer writes.

But frustratingly, the pilots never managed to see the object they were pursuing. After analysis of the aircraft's readings, "the Air Force's decision was that the evidence was insufficient to prove that there were real crafts in the air on that occasion," De Brouwer reports. Still, throughout 1990, the Air Force was asked — and could never specifically account for — the sightings, which, all told, numbered in the thousands by the time they quietly started going away again in April.

Three decades later, explanations are still in short supply, although some scientists now consider the event to be an example of mass hysteria. Dunning, quoting UFO skeptic Philip Klass, writes, "Once news coverage leads the public to believe that UFOs may be in the vicinity, there are numerous natural and man-made objects which, especially when seen at night, can take on unusual characteristics in the minds of hopeful viewers. Their UFO reports in turn add to the mass excitement, which encourages still more observers to watch for UFOs."

But De Brouwer still believes otherwise. "I can conclude with confidence that the observations during what is now known as the Belgian wave were not caused by mass hysteria," he says in UFOs. "The witnesses interviewed by investigators were sincere and honest. They did not previously know each other. Many were surprised by what they saw and today ... they are still prepared to confirm their unusual experience."

What we do know for certain is that there is a lot we don't yet understand about our universe. Even the U.S. Army has multiple stories of chasing strange, impossible objects through the sky. While the Belgian UFO wave likely wasn't a visitation by little green men, it remains without a satisfying answer even all these decades and technological advances later. "Today there is not yet any explanation!" Amond, the colonel who saw the lights with his wife, told Kean. "That is a pity, because I want to know before dying. Give me a correct explanation of my sighting; that is all I can ask."

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