Screenwriter Richard Matheson has said in interviews that he thought Charles Bronson was badly miscast.
American-International Pictures had planned on doing a sequel to this film. Concept drawings and even concept models were reportedly made. The sequel was not produced.
Richard Matheson combined two stories by Jules Verne for this screenplay: "Clipper of the Clouds" (1886) and its sequel "Master of the World" (1904).
The destruction of the British fleet is footage of the Battle of Trafalgar from That Hamilton Woman (1941).