36% of Americans believe in UFOs, that is, though most Unidentified Aerial Phenomena are actually explained as such mundane things as misidentified meteorological phenomena, astronomical phenomena, aircraft, and so on, there's ~ 5% that are as yet unexplained and that these unexplained UFOs are machines from somewhere other than Earth.
Have you ever observed a UFO that has never been sufficiently explained? Do you believe that some unexplained UFOs are machines from somewhere other than Earth? If so, why (what are your reasons or arguments for believing so)? What evidence is there to support your belief?