Sighting in Groslay, September 3, 2021

At around 6:30 pm, a lone witness noticed a small black dot very high in the sky, to their south-west. The sky behind it was clear, with no clouds in the background. The object looked round and very dark, described as "metal black", with no reflections and no other lights. It seemed to have appeared suddenly, leaving no trail or smoke. The witness watched it for at least 30 seconds. At first it seemed motionless, then it drifted very slowly toward the west.

The witness has no photo or video, but reconstructed the scene on a photograph and completed the questionnaire carefully. GEIPAN therefore rated the case's consistency as good, despite there being only one witness.

The investigation concluded that the witness had very probably seen a balloon, which was one of their own hypotheses. Three points support this: the round shape, the dark colour (explained by viewing the object against the light), and the slow movement in the direction of the wind. The sudden appearance is explained by the object's very small size, at the limit of visual perception. The apparent lack of motion came from a perceptual illusion caused by nearby clouds: the clouds seemed to move while the object was actually the one drifting. The case was classified A.