The "abandoned missile base" in the movie, is actually the Alabama Space and Rocket Center museum, and the "Rocket Park" is in the backlot of the museum. The museum benefitted from the filming of this movie, because the display rockets had to be "aged" for the film, and then later cleaned. The bi-annually cleaning of these outdoor displays is a major expense.
The matte painting over which the opening titles are shown was previously used to represent the ruins of New York City seen by the Army of Apes in Beneath the Planet of the Apes (1970).
The film was shot entirely on location in Alabama, USA.
Richard Harris and Ann Turkel were married during the time this movie was made and released. This picture was one of four films the couple made together, the others being Golden Rendezvous (1977), The Cassandra Crossing (1976), and 99 and 44/100% Dead! (1974), with the latter being made and released before they tied the knot.