Unidentified flying object (commonly abbreviated as UFO or U.F.O.) is the popular term
for any aerial phenomenon whose cause cannot be easily or immediately identified. The
United States Air Force, which coined the term in 1952, initially defined UFOs as
those objects that remain unidentified after scrutiny by expert investigators,[1]
though the term UFO is often used more generally to describe any sighting
unidentifiable to the reporting observer(s). Popular culture frequently takes the term
UFO as a synonym for alien spacecraft. Cults have become associated with UFOs, and
mythology and folklore have evolved around the phenomenon.[2] Some investigators now
prefer to use the broader term unidentified aerial phenomenon (or UAP), to avoid the
confusion and speculative associations that have become attached to UFO.[3] Another
widely known acronym for UFO in Spanish, French, Portuguese and Italian is OVNI.
Studies have established that the majority of UFOs are observations of some real but
conventional object—most commonly aircraft, balloons, or astronomical objects such as
meteors or bright planets—that have been misidentified by the observer as anomalies
while a small percentage of reported UFOs are hoaxes.[4] Only a small percentage of
reported sightings (usually 5 to 20%) can be classified as unidentified flying objects
in the strictest sense (see below for some studies).
Some scientists have argued that all UFO sightings are misidentifications of natural
phenomena[5] and historically, there was debate among some scientists about whether
scientific investigation was warranted given available empirical data.[6][7][8][9][10]
Very little peer-reviewed literature has been published in which scientists have
proposed, studied or supported non-prosaic explanations for UFOs. Allen Hynek was a
trained astronomer who participated in Project Bluebook after doing research as a
federal government employee. He formed the opinion that some UFO reports could not be
scientifically explained. Through his founding of the Center for UFO Studies and
participation at CUFOs he spent the rest of his life researching and documenting UFOs.
The movie Close Encounters of the Third Kind had a character loosely based on Hynek.
Another group studying UFOs is Mutual UFO Network. MUFON is a grass roots based
organization known for publishing one of the first UFO investigators handbooks. This
handbook went into great detail on how to document alleged UFO sightings.
UFO reports became frequent after the first widely publicized U.S. sighting, reported
by private pilot Kenneth Arnold in 1947, that gave rise to the popular terms "flying
saucer" and "flying disc." Since then, millions of people have reported that they have
seen UFOs.[11]
