Alleves 2014, two shapes in one observation

Summary

Three people in Alleves, in the French region of Haute-Savoie, observed an aerial phenomenon on December 21, 2014. Initially, from the window of their living room, they saw an elongated yellow shape moving across the sky. When they went out onto the terrace, they noticed a dark circular object that quickly disappeared. Although they used binoculars and naked eye observation, they could not identify the object. The strangeness of the case lay in the fact that the witnesses perceived two different phenomena that, at first, did not seem related. However, after an on-site investigation, researchers concluded that it was likely an aircraft contrail. The first observation corresponded to a sunlit contrail, while the second, darker one occurred when the aircraft was no longer directly illuminated by sunlight. This would explain the apparent transformation of the object.