Identification of UFOs

Main article: Identification studies of UFOs

Fata Morgana, a type of mirage in which objects located below the astronomical horizon appear to be hovering in the sky just above the horizon, may be responsible for some UFO sightings. (Here, the shape floating above the horizon is the reflected image of a boat.) Fata Morgana can also distort the appearance of distant objects, sometimes making them unrecognizable^[91]

Lenticular clouds have in some cases been reported as UFOs due to their peculiar shape

Studies show that after careful investigation, the majority of UFOs can be identified as ordinary objects or phenomena. The most commonly found identified sources of UFO reports are:

• Astronomical objects (bright stars, planets, meteors, re-entering man-made spacecraft, artificial satellites, and the Moon)
• Aircraft (aerial advertising and other aircraft, missile launches)
• Balloons (toy balloons, weather balloons, large research balloons)
• Other atmospheric objects and phenomena (birds, unusual clouds, kites, flares)
• Light phenomena mirages, Fata Morgana, ball lightning, moon dogs, searchlights and other ground lights, etc.)
• Hoaxes

A 1952–1955 study by the Battelle Memorial Institute for the USAF included these categories as well as a "psychological" one.

An individual 1979 study by CUFOS researcher Allan Hendry found, as did other investigations, that only a small percentage of cases he investigated were hoaxes (<1 %) and that most sightings were actually honest misidentifications of prosaic phenomena. Hendry attributed most of these to inexperience or misperception.