The Pentagon would have you believe that the truth is out there, although I am not entirely clear on when we started taking the Pentagon’s word for this stuff. I don’t know whether the truth is out there or not, but some days I suspect Robur the Conqueror is.
(Please Note: the film version of Master of the World features Robur’s much more generic airship from the prequel, Clipper of the Clouds. If you watch the film, you will get to see both Vincent Price and Charles Bronson doing their thing, but you won’t get to see any Steampunk Triple Changer that can function as an aircraft, automobile, and submarine.)