Paul Newman sometimes claimed he had had more fun making this film than any other.
Bears many plot similarities, similar scenes, and actors in common with
North by Northwest (1959), also written by
Ernest Lehman .
The film running on the TV as Craig finds the dying man is Bombshell (1933) staring Jean Harlow.
The Pan American jet on which Paul Newman arrives, a Boeing 707 (N704PA 'Jet Clipper Defiance') was an actual Pan Am aircraft, and it was the jet that delivered The Beatles to New York on their American debut on February 7, 1964.
In the driving scenes viewers can see that cars drive on the left side of the road, as in England. On September 3, 1967, four years after the release of this movie, Sweden switched to having cars drive on the right side of the road. Ironically, most cars shown have left-hand drive, anyway, as in America. The reason for this is that U.S. car manufacturers saw little profit in producing specialized right-hand drive models even for Britain and Japan, another left-hand drive nation, let alone the small Swedish market.