On the evening of November 5, 1990, between approximately 6:45 PM and 7:20 PM, a chain of unusual lights — later identified by multiple European space agencies as the re-entry of the Soviet Gorizont-21 (Kosmos-2099) satellite and its upper-stage booster — was observed in formation across the entire eastern half of France. Unlike a normal meteor or satellite re-entry, however, the 1990 event produced an extraordinarily large corpus of detailed eyewitness reports describing the lights as elements of a single enormous aerial structure: a solid dark mass seen against a brighter sky, with the re-entering pieces of debris appearing as illuminated 'windows' or 'ports' along the body of the structure. Witnesses across more than twenty départements reported what they described as a 'flying aircraft carrier' or an 'enormous triangular craft' passing slowly overhead.
The French Air Force Gendarmerie des Transports Aériens collected nearly 600 formal witness statements within three weeks. The GEIPAN investigation concluded that the majority of the reports were consistent with the satellite re-entry's visible track but that approximately 10% of the reports described genuinely anomalous phenomena — either an association of the debris with a separate, unexplained structured object, or completely separate sightings that occurred simultaneously by coincidence. The case remains formally classified by GEIPAN as a 'partially explained' event. Several witnesses' statements — particularly the series of detailed reports from the Vosges, the Côte-d'Or, and the Haute-Marne — are considered difficult to reconcile with satellite re-entry alone.
The November 5, 1990 wave is the largest single UFO mass-witness event in modern French history. It occurred at the peak of a period of intense European UFO activity (including the 1989–1990 Belgian Wave, which GEIPAN researchers consider formally related). The incident produced detailed reports from commercial airline pilots, French Air Force personnel, and gendarmerie officers across a 500-kilometre front. The case has been heavily studied by the CNES-based GEIPAN program and continues to be cited as an example of how genuine atmospheric phenomena (in this case a satellite re-entry) can apparently be accompanied by a parallel set of harder-to-explain reports.