The term foo fighter was used by Allied aircraft pilots in World War II to describe various UFOs or mysterious aerial phenomena seen in the skies over both the European and Pacific Theater of Operation. Thoug "foo fighter" initilly described a type of UFO reported and named by the U.S. 415th Night Fighter Squatron, the term was also commonly used to mean any UFO sighting from that period. Formally reported from November 1944 onwards, witnesses often assumed that the foo fighters were secret weapons employed by the enemy , but they remained unidentified post-war and were reported by both Allied and Axis forces . The phenomenon was never explained . Most of the information about the issue has never been released by military intelligence.