ANCINNES (72) 21.01.2017

On 21 January 2017 in Ancinnes (72), 3 witnesses observed what appeared to be a stationary greyish object in the sky. Their photograph is characteristic of a horseshoe-shaped aircraft contrail. GEIPAN explains that exhaust plumes diverge from the fuselage before joining in the wake. An aircraft travelling away from the witness, rather than across the line of sight, allows the 2 trails to remain separately visible for longer. The unusual appearance arose from the lighting. Contrails are often bright in direct sunlight; here the Earth blocked sunlight from reaching the trail, while a higher area of sky behind it remained sunlit, making the trail stand out against a brighter background. The photograph visibly becomes brighter towards the top. Flightradar showed several possible aircraft in the reported direction, southeast of Ancinnes near Alençon, after 18:10 local time, 17:10 UTC. One track very probably corresponded to the UAP: the aircraft was seen from below and behind, giving the horseshoe its upward orientation. That track was also within the area no longer lit by the Sun. The attached reconstruction document details these explanations. The witnesses reported about 10 minutes, which GEIPAN considers inconsistent with an aircraft trail that would change considerably during that time. It concludes that the observation was shorter and the duration overestimated, a common error. The witnesses' 2 photographs, taken 1 minute apart, moreover show different trails. GEIPAN classifies the case A: observation of aircraft contrails.