Pilot witness in Seine-et-Marne, France

On June 5, 2017 (not 2015 as mistakenly stated by the witness in the free text) between 11:58 a.m. and 12:03 p.m., a witness observes in the clear sky a phenomenon that intrigues them. The witness sees to the North/West at medium altitude, 2 lights projected side by side, like 2 headlight beams. They distinguish behind these two headlights a sort of cylindrical fuselage, the whole thing moving Eastward horizontally. "The sort of vessel" moves at airplane speed at low altitude, then stops a first time in what seems to be stationary flight, then climbs in altitude almost vertically. A commercial airplane at medium altitude comes from the North-East and seems to cut across the initial trajectory of the "vessel." The airplane continues its heading, the "vessel" resumes its horizontal flight with its original heading; then seems to stop a second time, to again climb in altitude almost vertically, until it completely disappears from the witness's view. The witness thinks they are dealing with an unknown vessel that may have been disturbed in its trajectory by the medium-range airplane and asks GEIPAN to investigate. Only one testimony is collected. As the attached air traffic record indicates, the witness is located in a high-activity zone (at least at that hour) with airplanes at all altitude levels, including light aircraft doing rotations at low altitude. Under these conditions, one does not see where the strangeness would lie in the description given by the witness. An airplane at low or medium altitude is distinguishable by its lights (which can be turned on during the day too) and by its fuselage. The airplane at low altitude can perform all types of maneuvers (for example training maneuvers) including speed reductions, heading changes interpretable by the witness as strong speed reductions (as soon as the heading changes from "transverse to the line of sight" to "along the line of sight") as well as sudden altitude changes. Stationarity or vertical climbs can hardly be assessed from the ground; moreover, the witness uses the words "it seems" or "almost." Under these conditions, the strangest thing in all of this is indeed the scenario the witness constructs by imagining that the low-altitude airplane is an unknown vessel that changes its trajectory to escape the trajectory (or the vision?) of the commercial airplane. Since it is verified (here the aeronautical context analysis is sufficient) that the observation itself reports nothing strange, GEIPAN does not devote more resources to exploring or invalidating the scenarios put together by the witness to interpret or explain a strangeness that has no reason to exist. Note, if necessary, that the observation is made in broad daylight, in an urbanized area, and that therefore a real strangeness would hardly have gone unnoticed by the large number of potential witnesses on the ground and... in flight. Finally note that the same witness gave a testimony of the same type two months later (EMERAINVILLE (77) 04.08.2017). Consequently, GEIPAN classifies the case as A: airplanes.