The Belgian UFO wave refers to a series of sightings of triangular UFOs in Belgium, which lasted from November 29, 1989 to April 1990.
The Belgian UFO wave peaked with the events of the night of 30/31 March 1990. On that night unknown objects were tracked on radar, photographed, and were sighted by an estimated 13,500 people on the ground - 2,600 of whom filed written statements describing in detail what they had seen. Following the incident the Belgian air force released a report detailing the events of that night.
After some researches my conclusion is that there are too much serious witnesses in this case and it is probably true.