An account in Essonne, France

On November 6, 2011, at around 1 p.m., a witness notices in the sky the presence of a ball that he describes as the size of a pinhead, orange in color but dull. It seems stationary at a high altitude, but one that remains difficult to assess. The witness looks away for a moment and will not find the object in the sky again. The observation lasted 10 seconds. No other testimony will be collected. The hypothesis of an orange party balloon flying at about 500m seems to explain this observation. Its apparent immobility can be explained on the one hand by the fact that, even if the balloon goes at the speed of the ground wind (30km/h), at 500m that gives an apparent angular displacement speed of about 1°/s, a speed difficult for the human eye to appreciate against a uniform sky background near the zenith, and on the other hand the wind at 500m is not always the same as on the ground. Since helium-filled party balloons generally burst fairly quickly during their ascent to altitude, the sudden disappearance of this balloon is quite normal. This case is therefore classified "B": probable balloon.