SILLY-LE-LONG (60) 31.05.2015

On 31 May 2015 at about 00:50–00:55, two witnesses on duty in a van (T1 driving and T2 in the passenger seat to his right) were in Silly-le-Long (60), joining the N2 expressway heading northeast toward Nanteuil-le-Haudouin (60). The night was clear and the Moon was behind them. As they drove, they noticed intriguing steady white and flashing red lights at low altitude. Familiar with the area near Roissy airport, they regularly saw aircraft, but these lights seemed much too low and apparently stationary, which struck them as abnormal. Slowing down, they saw a large, dark V-shaped UAP to their left. Just after passing the bridge known as the Silly bridge, only T1 could see it. They observed it while driving, through the windshield, window or rearview mirror, for between one and less than four minutes, until the descending road and surrounding terrain hid it from view. Their accounts were recorded in an official gendarmerie report and a GEIPAN questionnaire. No other accounts were collected. This particularly interesting case required considerable work by GEIPAN and ultimately became an instructive example in several respects, detailed below and in the attached investigation report. The witnesses saw horizontally arranged white and red lights ahead of their vehicle, apparently stationary. When they drew level with the phenomenon, they saw a large object shaped like a very flattened V. The main source of perceived strangeness, and the reason for reporting it, was the impression of a triangular object hovering motionless: they considered it could not be an airplane because it was stationary, and it did not look like a helicopter. The investigation established that a light aircraft practicing touch-and-go landings was flying at low altitude in the opposite direction to the witnesses' vehicle. Extensive work, including an on-site reconstruction with the witnesses and 3D simulations using the aircraft's GPS navigation data and the vehicle's route, demonstrated a pivot effect. The line joining the witnesses and aircraft essentially rotated about a fixed pivot, potentially giving witnesses viewing the aircraft the impression that it was stationary at that point. This effect was particularly clear and consistent with their visual observation when they passed closest to the UAP. The pivot was at a bridge over the road, also the location where they saw the apparently stationary UAP. The reconstructed angular position of the aircraft was close to the reported UAP positions for much of the sighting. The discrepancy could reach 20–30°, especially just after the bridge, but this remained compatible with an error of perception or memory, particularly since the two accounts themselves differed by a similar amount. This was a key element supporting misidentification of the aircraft. Furthermore, the witnesses did not distinguish a separate airplane from the UAP, although, if they were different objects, the lit aircraft would have been only 20–30° away, visible on a clear night at a distance of a few kilometers, or much less near the pivot. Likewise, the aircraft's pilot, when interviewed, had noticed no large object of the kind described, emitting lights bright enough to be seen several kilometers away, immediately beside his landing approach. These facts alone would support classification as a misidentification of the identified aircraft. Nevertheless, significant discrepancies between the reported observation and the aircraft's appearance prompted further analysis. - Some reported lights could not be explained by the aircraft's lights in terms of color or whether they flashed. However, the largest lighting discrepancy came from T1 and could be attributed to misperception. In particular, after the bridge T1 saw slowly flashing white luminous rectangles where there should have been point-like flashes from the aircraft's coded flashing lights. - The main discrepancy was angular size: the aircraft would have subtended 0.7° at the reported observation point, whereas the witnesses' estimates reconstructed by different methods ranged from 14° to 27°. Overestimation of UAP angular size is common, but this difference was very large. However, these estimates were made in absolute terms or without reliable reference to objects on the ground. The most emphatically reported angular discrepancies also came solely from T1: the white lights differed from the aircraft both in their rectangular appearance and their angular separation. He was then beyond the bridge, observing under conditions that were uncomfortable and unfavorable to accuracy: at night, looking backward while driving, largely through the rearview mirror. Because of these discrepancies, the entire case was submitted to GEIPAN's expert panel. The evidence favoring aircraft misidentification prevailed, and a majority of experts accepted a substantial perceptual illusion, considered explicable through night driving, observation in a mirror, and fatigue or stress. Nevertheless, the discrepancies were significant enough to be recorded in GEIPAN's database to inform current or future work on perception and memory, whether specific to UAPs or otherwise. GEIPAN therefore classifies the case A: misidentification of an airplane. The first 3D simulation video contains several synchronized windows: - Main screen: a simulation of the view from the witness's vehicle, showing the UAP as described and the aircraft according to its recorded GPS positions. The aircraft's pivot effect is clear, especially when passing the bridge. A vertical purple arrow marks the pivot. - The UAP's visual appearance is based mainly on T1's descriptions. Its position differs from the aircraft's, and its angular size differs before and especially after the bridge. The two red reference markers point to nothing in particular; the interval between them represents an angular separation of 20°. - Bottom-right window: footage from the vehicle during a daytime reconstruction. - Bottom-left window: a close-up of the aircraft simulation. The other 3D simulation video shows the scene from above. Naturally it does not show the witness's view of the UAP, but allows the pivot effect to be appreciated.