The fictional airliner in this movie is a DC-7, substantially altered to look like a contemporary jet airliner, but not resemble any that actually existed. Because of the theme (and to avoid spoiling an excellent ending), no airline or aircraft manufacturer would have anything to do with the movie, and any resemblance to an actual aircraft would invite litigation. Curiously, there are aspects to the fake wings that are almost 30 years ahead of their time.
Jane Russell considered herself semi retired at this time and agreed to do a cameo for her friend Aaron Rosenberg.
Rod Taylor was made to look older in the present time scenes so that he looks his actual age during the wartime flashbacks.
Charlton Heston was offered the lead role on the same day he was offered roles in both The Satan Bug (1965) and The Agony and the Ecstasy (1965). He chose to play Michelangelo in the latter.
Ernest K. Gann, who wrote the non-fiction book on which the film was putatively based, later claimed he was so unhappy with the end result that he had demanded his name be removed. However, it remained.
Dorothy Malone: as Lisa Bond. Malone did a true short scene cameo with Rod Taylor. In pre-movie reviews, viewers wanted more of her, so they brought her back for another scene, but the onscreen credits had already been finished.