Sighting in Louviers, September 17, 2017

Between 10 pm and 11 pm, a witness was at home on the top floor of an apartment building in a built-up area, lying on a mattress on the floor and looking at the sky through the window. Three faint lights arranged in a triangle appeared, and their unusual look caught the witness's attention. Against a cloud, the witness then made out the dark outline of a triangular object. As the object was about to leave the window's field of view, the witness got up to open the window. The object quickly disappeared behind the roof of the building. The sighting lasted less than 10 seconds. The lights were orange-yellow and dim. The night was dark, with scattered cloud and light to moderate wind. Only one witness account was collected.

The investigator considered three hypotheses: Thai lanterns, a civil or military aircraft, or a civil or military drone. Lanterns matched the description in part (several faint lights moving together, perceived as a single object), but the wind blew opposite to the object's path. A civil aircraft was ruled out: the viewing angle from the window did not allow a good view of aircraft on the nearby air route, and those on the radar returns were heading the wrong way. A military aircraft flying very low from the air base to the south could have explained the look of the lights, but the witness, with the window open, would have heard the engines, and no military flight was confirmed. For a drone, the south-to-north path could point to that base, but there is no authorized overflight zone near the site, especially at night, and no drone flight was confirmed. The trajectory itself was straight and at constant speed, with nothing odd about it.

The object's appearance (three faint lights in a triangle around a dark mass) remains unexplained by these hypotheses. With no other witness, photo, video or precise timing, the case was classified C: insufficient data.