BELGIAN.

The first major event near Eupen included observations by some 30 gendarmerie officers, including patrolmen Heinrich Nicoll and Hubert von Montigny, who watched a low-flying triangular object with three downward-facing white lights and a central red light hover and move slowly across the countryside. Over the following 18 months, the Belgian gendarmerie collected more than 2,000 written sighting reports.

On the night of March 30–31, 1990, ground radar at Glons and Semmerzake detected unknown traffic and the Belgian Air Force scrambled two F-16 fighters. Pilots achieved repeated radar locks on objects that exhibited extreme velocity and acceleration changes — at one point reported as descending from 10,000 feet to 500 feet in seconds. The pilots could not visually acquire the targets. The radar tapes from the encounter were released by the Belgian Air Force.

Belgian Air Force Major-General Wilfried De Brouwer, then chief of operations, took the unprecedented step of holding press conferences acknowledging the events as genuine unexplained intrusions of national airspace. He later stated publicly: "The Belgian Air Force has been confronted with a fact that it cannot explain." A widely circulated 1990 photograph of a triangular craft taken in Petit-Rechain was eventually admitted by its author Patrick Maréchal in 2011 to have been a hoax, which removed one piece of imagery — but did not affect the underlying radar and pilot data, which remain unexplained.

The Belgian Wave is unusual in the history of European UFO events because of the institutional candor of the Belgian government. The Air Force collaborated openly with the civilian research society SOBEPS, which published two extensive volumes of case data. The events remain officially unexplained in the public record.