Sighting in Ancinnes, January 21, 2017

Three witnesses saw a greyish object in the sky, which seemed motionless to them, after 6:10 pm local time. It was to the south-east of where they stood. They took a photograph and estimated that the observation lasted about ten minutes.

The investigation recognised the photo as showing a horseshoe-shaped aircraft contrail. This shape forms when the exhaust trails spread away from the fuselage before merging again in the aircraft's wake. The plane was flying away from the witnesses, so the two trails stayed visibly separate for a long time. The sun was no longer lighting the trail directly, as it lay in the Earth's shadow. It stood out, however, against a higher part of the sky that was still sunlit and therefore brighter, and the photo does show brightness increasing towards the top.

Flightradar showed several aircraft in that direction at that time. One flight path very probably matched the phenomenon: the plane was seen from below and behind, which explains why the horseshoe opened upwards, and its path lay in the area no longer lit by the sun. A duration of ten minutes does not fit a contrail, since an aircraft moves a great deal across the sky over that time. The duration was overestimated, which is a common mistake. In addition, the two photos taken one minute apart do not show the same trail. GEIPAN therefore classified the case as A: observation of aircraft contrails.