The vanishing man (1997)

While Nick Cameron is returning to England from the continent with mysterious cargo in the cabin section of his small aircraft, he is thrown off-course by a severe electrical storm and loses radio contact. To his surprise and horror, he is arrested upon landing and accused of being a traitor in connection with the cargo he has been carrying - which, unknown to him, contained plutonium. Although he pleads innocent, Nick is not believed and is sentenced to a long term in prison. While in prison, he is subjected to special experimentation at a mysterious laboratory - with one unnerving, and unexpected, side-effect of the experiments being intermittent invisibility. —David McAnally