UFOs And Aliens (Conspiracy) 

An unidentified flying object, or UFO, is any real or apparent flying object which cannot be identified by the observer and which remains unidentified after investigation. The term flying saucer is also sometimes used.

Reports of unusual aerial phenomena date back to ancient times (see Ancient astronaut theories), but reports of UFO sightings started becoming more common after the first widely publicized United States sighting in 1947. Many tens of thousands of UFO reports have since been made worldwide.[citation needed] Many more sightings, however, may remain unreported due to fear of public ridicule because of the social stigma surrounding the subject of UFOs and because most nations lack any officially sanctioned authority to receive and evaluate UFO reports.

Once a UFO is identified as a known object (for example an aircraft or weather balloon), it ceases to be classified as a UFO and is reclassified as an identified object.

Source: Wikipedia