Recently I saw film Fire in the Sky. At the beginning it was written:
Based On a True Story
Does it mean that Travis Walton was really abducted by aliens?
It is based on the claims of Travis Walton that he was abducted. Whether the story is "true" or not is dependent upon whether you believe the story or not. Some do not believe it.
Travis Walton is an American logger who claims to have been abducted by a UFO on November 5, 1975, while working with a logging crew in the Apache-Sitgreaves National Forest in Arizona. Walton could not be found, but reappeared after a five-day search. The Walton case received mainstream publicity and remains one of the best-known instances of alleged alien abduction.