An Unidentified Flying Object, or UFO, is the popular term for any aerial phenomenon that cannot immediately be identified. Some definitions, such as the one used by the USAF, define a UFO as an object unable to be identified after scrutiny.
UFO Evidence : http://www.ufoevidence.org/
UFO drone analysis : http://www.kbvp.com/ufo-drone-analysis
UFO Drone Video : http://www.metacafe.com/watch/845277/ufo_drone_video/
