UFOS shaped like mysterious black triangles or diamonds have been repeatedly spotted flying over Britain and Europe.
The objects were intercepted by fighter jets in Belgium, tracked by a NATO radar travelling at incredible speeds, and one potentially even crashed at an RAF base.
Shapes in the sky appear to have menaced the airspace over Northern Europe for the better part of a decade - and there has still be no answers as to what they may have been.
"It is still a genuine mystery - these triangle sightings in the 80s and 90s are significant, but still unexplained, " former Ministry of Defence UFO investigator Nick Pope told The Sun Online.
Was it all an elaborate hoax? An example of mass panic? Alien spacecraft? Repeated misidentification of conventional planes? Or perhaps top secret US technology?
Britain always denied it was aware of any experimental US aircraft operating in its airspace - but declassified documents show Whitehall feared it was being kept in the dark by the Americans.
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