Unidentified flying object ( UFO ) Aliens
Though the term ExtraTerrestrial Vehicle (ETV) is used for only a small subset of UFO studies  for many people the term UFO is positively associated with alien spacecraft and many discussions of UFOs revolve around this presumption.. While serious UFO researchers maintain that Extraterrestrial Intelligence (ETI) as a cause for UFOs remains a speculative hypothesis only, nevertheless many UFO enthusiasts, contactees, and devotees have created organizations and religions (for example The Church of Scientology) that have adopted extraterrestrial themes. It is therefore fair to state that in general the extraterrestrial UFO concept has evolved into a prominent mythos in modern culture.
A popular misconception is that UFO sightings by the masses increased precipitously after a widely publicized incident reported by businessman pilot Kenneth Arnold in 1947 (a sighting that also gave rise to the popular terms "flying saucer" and "flying disc"). However mass public reports, or "UFO waves", were also recorded in the U.S. in 1886, 1897, 1908-1916, 1909, 1913 and 1946. While some studies have established that most UFO sightings are misidentifications of mundane objects — most commonly aircraft, balloons, or astronomical objects such as meteors or bright planets — and a percentage of reported UFOs are the result of hoaxes  in the largest study of its kind ever conducted, the Battelle Institute's Project Blue Book Special Report No. 14 (1955), concluded that more than 21% of the nearly 3000 reports it analysed remained designated as "unknown"  - that is, unable to be explained in mundane terms.
Nevertheless the mere possibility that all UFO sightings are misidentifications of known natural phenomena coupled with a general perception of a paucity of empirical data, has inspired some debate in the scientific community about whether scientific investigation was or is warranted . Very little peer-reviewed literature has been published in which scientists have proposed, studied or supported non-prosaic explanations for UFOs. Nevertheless, UFOs as a cultural phenomenon continues to be the subject of serious academic research and amateur investigators continue to advocate that UFOs represent real but unexplained events.