The Reluctant Astronaut (1967)

He's an Astro-Knott Turned Astronaut in the Maddest Mix Up in Space History!!

Don Knotts is Roy Fleming, a small town kiddie-ride operator who is deathly afraid of heights. After learning that his father has signed him up for the space program, Roy reluctantly heads for Houston, only to find out upon arriving that his job is a janitor, not an astronaut. Anxious to live up to the expectations of his domineering father, Roy manages to keep up a facade of being an astronaut to his family and friends. When NASA decides to launch a lay person into space to prove the worthiness of a new automated spacecraft, Roy gets the chance to confront his fears.