Unidentified flying object

unusual apparent anomaly in the sky that is not readily identifiable

A UFO (Unidentified Flying Object) is any object flying in the sky which cannot be identified by the person who sees it. Sometimes the object is investigated. If people can still not figure out what the object is after an investigation, it is called a UFO. If they figure out what the object is, it can no longer be called a UFO because it has been identified.

A UFO in New Jersey, USA
UFO landing strip in Cachi, Argentina
UFO, Jakobsdal, Linköping, Sweden

Even though UFOs might have different origins, people often use the word UFO when they are talking about alien spacecraft. Flying saucer is another word that is often used to describe an unidentified flying object. Some UFOs that are seen in the water, or going in or out of the water are called USOs (Unidentified Submerged Objects).

Identified flying objects (IFOs)


Studies estimate that 50-90% of all reported UFO sightings are identified later. Usually 10-20% are never identified. Studies also show that very few UFO sightings are hoaxes (people trying to trick other people). Most UFOs are actually natural or man-made objects that looked strange.

80-90% of IFOs are identified as one of three different things:

  1. astronomical causes (for example: planets, stars, or meteors)
  2. aircraft
  3. balloons (including weather balloons)

10-20% of IFOs are other causes (such as birds, clouds, mirages, searchlights, etc.)


  • Allan Hendry, The UFO Handbook: A Guide to Investigating, Evaluating, and Reporting UFO Sightings, 1979, Doubleday & Co., ISBN 0-385-14348-6

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