A UFO becomes an IFO when it is positively identified as a known object. The following is a partial listing of IFO’s that can be reported by witnesses as UFO’s. Depending upon whom you consult, the percentages of IFO’s making up UFO reports will differ. Sceptic organizations such as CSICOP (aka CSI) will argue that all UFO sightings are in fact IFO’s, and that it is missing clues that prevent making a positive identification with all cases. It is the cases that cannot be explained by the following that intrigue UFOlogists.
Common causes of misidentification
Venus, Jupiter, the rising moon etc.
Venus in particular is a common culprit as it can be intensely bright and will twinkle differing colours under the right atmospheric conditions.
Comets and Meteors
The media usually provides ample coverage of a comet’s approach and dates of larger meteor showers are fairly well known by the public. Larger meteors known as fireballs are often reported as well.
Lenticular clouds are quite strange in appearance and can be mistaken for “saucers,” Water droplets can create the illusion of metallic colouring when struck by sunlight at certain angles.
Rocket boosters etc are seen as an unexpected bright light in the sky upon re-entry.
The NOSS (National Ocean Surveillance System) in particular have been found to be the causation of some UFO reports.
Airplanes, Gliders, Helicopters, Blimps, Balloons
Military, commercial, and private. Many company’s are developing and testing unmanned, strange looking aircraft that will be able to perform maneuvers that conventional aircraft cannot.
Birds and Insects
Fireflies and migrating spiders have been reported as UFO’s. An interesting story is of owls that became covered in phosphorescent fungus while roosting in infected trees and later being reported as “ghostly lights.”
Other natural causes include: the aurora borealis, lightning, and mirages.
This list is far from complete, but gives the reader a good idea of what competent investigators will consider while investigating UFO reports.