Pilot witness in Yvelines, France

On April 12, 2015 between 1:30 PM and 2:15 PM, a witness on a terrace was watching planes high in the sky when he saw a dark object shaped like a flattened lens moving very quickly at low altitude on a straight trajectory. The object disappeared from the witness's view, hidden by the landscape. Only one testimony was collected. A radar air traffic record was requested from military air traffic control. The resulting tracks were overlaid on a Google Earth map (with an accuracy of around 500 meters): one can indeed see fairly significant air traffic of small planes flying under visual flight rules (VFR), including one particular trajectory that seems to fit the observation quite well (see the radar map document, and in particular the red track that passes from East to West of Plaisir from 12:10:48 UTC (2:10 PM local) to 12:12:18. This aircraft climbs slowly from East to West from 400m (Z12) to 500m (Z16), and flies at around 160 km/h (89 to 75 knots). Its passage in front of the witness would have lasted less than a minute, compared to the 30 seconds of observation indicated by the witness. This aircraft, probably small, appeared to the witness to be farther away, and therefore faster than it really was. Since the witness was looking toward the South, close to the time of the zenith, the aircraft in backlight necessarily appeared black to him. Due to the low angular elevation, the wings, seen edge-on, could be invisible. GEIPAN classifies this case as B: probable observation of a small plane in visual flight, at low altitude, seen against the light. Due to the uncertainty about the time of the observation, this case is not classified as A.