 Thus when carefully studied, a substantial fraction of reports (given the available data) is currently not understood.Fata Morgana, a type of mirage, may be responsible for some flying saucers sightings, by displaying objects located below the astronomical horizon hovering in the sky, and magnifying and distorting them.Similarly some unidentifieds seen on radar might also be due to Fata Morgana-type atmospheric phenomena, though more technically known as "anomalous propagation" and more commonly as "radar ghosts".