FREJUS (83) 25.08.2017

On 25 August 2017 at 02:15, a time confirmed by T2, 2 witnesses noticed red and green lights in the night sky. Initially stationary, they moved together, changed course and were soon hidden by the landscape. No sound was heard. GEIPAN considers an aircraft very probable, with red and green navigation lights. The lights were side by side or adjacent. During the final movement to the right, only green remained, as expected when an aircraft crosses rightwards at low elevation and its fuselage hides the left red light. It then disappeared behind trees. T1 rejected aircraft and helicopters because there was neither sound nor flashing. GEIPAN notes that sound depends on distance—the UAP may have been farther away than assumed—and wind. Météociel recorded an easterly wind opposing sound from the west, the viewing direction. Intense attention to an unusual visual impression can also reduce attention to, or recollection of, sound; GEIPAN has many such examples. The source explains that red and green navigation lights are steady, whereas white anti-collision strobes flash; it states that navigation lights are required throughout flight, but strobes are not. The absence of flashing is itself uncertain for part of the sighting, since T2 said, “Then I also saw a green light flashing.” GEIPAN considers the positive lighting evidence strong and the silence and flashing objections debatable and inconclusive. The stationary and oscillating behaviour particularly favours a helicopter: initially mainly its left side and red light, then a partial turn showing both colours, followed by departure to the right showing only the green right-side light. No matching aircraft appears in commercial traffic records, but those records are not wholly reliable and helicopter operations are often non-commercial. A private, civil-protection, medical-transport or military flight is therefore suggested. The request to CNOA air-traffic services for radar traces came too late, and GEIPAN notes that low-altitude flights such as this may leave no radar trace. GEIPAN classifies the case B: very probable aircraft observation.