According to abbreviationfinder, the term UFO, an acronym for ‘ unidentified flying object ‘ refers to the sighting of a flying object, real or apparent, that cannot be identified by the observer and whose origin remains unknown after investigation. [one]
The acronym is a carbon copy of the English UFO (unidentified flying object: ‘unidentified flying object’).
Brief historical account
Although archaeoastronomy has provided anecdotal evidence that the UFO phenomenon dates back to antiquity, it was not until 1947 that an international wave of sightings took place after on June 24 of that same year the American civilian pilot Kenneth Arnold saw, while was flying, a formation of nine very strange aerial devices near Mount Rainier, in the state of Washington (United States). Since then, several million people claim to have seen UFOs, tens of thousands of photographs and films have been taken, thousands of footprints have been found on the land of half the world and a multitude of contactees and abductees have been investigated.
Characteristics of UFOs
The observed UFOs have the following characteristics: 
- Absence of smoke and exhaust (except for some faint wake observed in some cases).
- Absence of noise, that is, they do not produce the classic supersonic “bang” of jet aircraft. Only a faint hum has been reported at takeoff and landing times.
- Brilliant luminosity with colorvariations.
- Metallic or light-reflecting surface.
- Diversity in 160 different ways. From inverted “flying saucers” (seen by Kenneth Arnold on June 24,1947) to triangles, rectangles, “ amoebas ”, “ jellyfish ”, and “ clouds of fire ”. Predominating the elliptical, cylindrical or circular shape, flat at the bottom and rounded at the top.
- The first observed had windows.
- Small speeds and the ability to remain static for a long timeat a point in space without any motor or apparent noise. (they override the law of gravity).
- Amazingly high speeds in each era: in the 1950s they were traveling at 3,200 km/h (2.6 Mach), the dishes observed by Ken Arnold; in the following decade the UFOs reached 14,000 km/h (11.4 Mach) those seen in the Gulf of Mexico on December 6, 1962.
- Various sizes: from 1.5 meters in diameter (Lowest off and Southampton, England, 1962 – 1963) to 1,200 meters in diameter (New Mexico, October 16, 1957).
- Incredibly sharp changes of direction and sense. (Annul the Law of Inertia). Maneuverability that far exceeds ground fighter aircraft.
- Ability to remotely project a “double” image of itself that confuses pilots. Example: the pilot sees the UFO in front of his plane, while the radar operator in the control tower is seeing the UFO above the plane(30 January 1985, Minsk).
- Ability to instantly appear or disappear at a point in space, where it was at rest. (Sudden jump). (Phoenix, 2000).
Ufology (tracing from English ufology, word formed from the acronym UFO (unidentified flying object), in Spanish “ovni”, ”Objeto Volador No Identificado”),  also known in Spanish as ufology, is the study of the UFO phenomenon from the analysis of the material related to it: photographs, videos, alleged testimonies about sightings, radar reports, etc., in order to propose hypotheses about its origin.