The Brézolles Mylar Balloon Incident

On May 27, 2023, at approximately 08:15, a single witness observed a luminous point in the sky from their residence in Brézolles, located in the Eure-et-Loir department of France. The object appeared to the left of the sun and exhibited what the witness described as atypical movements. The object traveled on an apparent trajectory from north to south, progressively moving to the right relative to the observer's position. After a brief stop—which the witness considered the most unusual aspect of the sighting—the object resumed its trajectory, continuing rightward before disappearing from view. The witness described the object as round, grey in color, and comparable to a metallic object, noting it reflected sunlight. GEIPAN (the French National Center for Space Studies' UFO investigation unit) conducted a thorough investigation, collecting complete data including azimuths, elevations, and apparent size measurements. However, the case was rated as having medium consistency due to relying on a single witness account with no photographic or video evidence. Air traffic data from CAPCODA (French Air Defense Operations Center) showed only routine high-altitude commercial activity with nothing anomalous. Meteorological analysis using the high-resolution AROME weather model confirmed wind conditions at moderate altitudes below 250 meters that were consistent with balloon movement. The official investigation concluded with high confidence that the witness observed a festive mylar balloon carried by wind currents. The calculations of distance, size, and velocity aligned with the characteristic parameters of a wind-borne party balloon. The perceived sudden stop was attributed to brief local variations in wind speed at altitude—variations that can occur but may not be detectable even with high-resolution meteorological models. GEIPAN assigned this case a classification of 'A', their highest certainty level for explained phenomena, definitively identifying it as a mylar party balloon.