UFOs, strictly meaning unidentified flying objects as defined by the U.S. Air Force, have been observed. The majority of UFOs are later identified, explaining any odd characteristics perceived by original witnesses. The existence of UFOs as transport or proof of extraterrestrial life has never been proven.
In the 1950s, during the Cold War, the U.S. Air Force created the term "UFO," originally "UFOB," to describe occurrences of mysterious objects seemingly hovering or moving rapidly through the sky and requested that observations be reported. The stated objectives were to assess threats to national security and determine the technical aspects involved. Ninety to 95 percent of all UFO encounters reported have been explained, while the rest remain unexplained, with insufficient evidence. Scientists are fairly certain that extraterrestrial life does exist somewhere within the vastness of the universe, but the probability that any of those life forms are civilized or capable of visiting Earth is very slim.