When Eddie Valentine and his gang learn that Neville Sinclair is a Nazi, they quit working for him and join up with the FBI agents against the Nazi thugs hidden in the shadows. This reflects the attitude of real-life American gangsters during this era, in that they did not like fascism, particularly because Benito Mussolini persecuted the Sicilian Families back in the Old Country. Nor did any Jewish mobsters like Adolf Hitler. In fact, organized crime was one of the biggest allies the American government and law enforcement had when it came to rooting out Nazi spies and collaborators.
The plane flown by Cliff in the opening is the Gee Bee racer, specifically Model "Z" from 1931. It was built by the Granville Brothers Aircraft Company (brothers Zantford, Thomas, Robert, Mark, and Edward), hence the plane's initials "G.B." The R-1 was for a time the fastest land-plane in the world, essentially a cockpit, wings, and tail built around an 800 hp Pratt & Whitney Wasp engine. James Doolittle (who would lead the bombing raid over Tokyo in 1942) won the 1932 Thompson Trophy race flying a Gee Bee R-1 at a speed of 252.686 miles per hour.
During the fight scene on board the zeppelin Cliff says to Neville, "Where's your stuntman now Sinclair?" which Neville replies "I do my own stunts." This line is in reference to Timothy Daltons time as James Bond, since he is known for being the only Bond actor to perform most of his own stunts in "The Living Daylights" and "Licence to Kill".
Billy Campbell, who once studied commercial art, made sure to read the Dave Stevens graphic novel on which this film was based. He got the part after getting a haircut to make himself look identical to the character in the graphic novel.
The original inventor of the rocket pack was thirties pulp novel hero Doc Savage, the Man of Bronze, in the original graphic comic book by Dave Stevens. However, because licensing considerations, Disney did not seek permission from Conde Nast, the copyright holder of Doc Savage, and opted to substitute Doc Savage with the flamboyant billionaire Howard Hughes.
In the original graphic novel, Cliff Secord's girlfriend is called Betty Page, not Jenny Blake. Dave Stevens (the creator of the comic novel) based the character "Betty Page" upon his real-life friend, 50's pin-up girl Bettie Page. She would not allow her name to be used in the film.
In the South Seas Club, Neville Sinclair, a Nazi, greets Clark Gable. This is based on the little known fact that Gable was Adolf Hitler's favorite actor. During WWII, Hitler offered a sizable reward to anyone who could capture Gable and bring him to Germany alive and unscathed.
Disney had a special mechanism built especially for this film. Called the "Shaky-cam", it was designed to be the exact opposite of the "Steady-cam", that is, to introduce vibrations into the picture. This was used in the scenes filmed inside the Zeppelin to give the impression of the power of the engines. When the movie went to video, the effect didn't transfer too well, and was therefore steadied.
The Gee Bee racer was nicknamed "The Widowmaker" and "The Flying Coffin" because it was incredibly difficult to fly and was prone to crashing. Because of its speed and maneuverability some pilots raced it in spite of the danger.
The real Dog Café (the café shaped like a Bulldog) was built in 1928 on West Washington Boulevard but destroyed by weather in the mid '70s. A replica has been a part of the "Streetscape" in the Petersen Automotive Museum since its opening in 1994.
The reproduction of the Gee Bee racer flown by Cliff Secord is currently on display at the Museum Of Flight in Seattle, WA. The original Gee Bee this aircraft was based on was painted in the same color scheme as the one used in the movie, however the original was named the "City of Springfield" and was flown by pilot Lowell Bayles. Bayles flew barefoot, as he said it gave him a better feel of the rudder. He was killed flying this airplane while making a record speed attempt in December 1931.
'Tiny Ron''s character Lothar is made-up to look like Rondo Hatton who played similar characters in the "B" movies which inspired The Rocketeer (1991). Ron can be seen out of makeup in a cameo as one of two Good Old Boys. He gapes as his companion marvels at the "Big gopher!"
The actual Gee Bee used in filming was only allowed to land a very limited amount of times during it's time working on the movie as landings are extremely hard on the landing gear of this particular plane.
The trivia items below may give away important plot points.
The model that Cliff glides with to escape from Howard Hughes's warehouse resembled "The Spruce Goose", a plane built by Hughes which was so huge that many people doubted it would ever fly. This explains his "It does fly!" comment. At the time the film was made, Disney owned the Spruce Goose, and it's rumored that they placed this part in the film as a promotion for that attraction, which (apart from the Queen Mary) was the only money losing Disney attraction in the US.
One of Neville Sinclair's final lines is "I'll miss Hollywood" - and he does, as he crashes into the "land" portion of the "Hollywoodland" sign, which is now the "Hollywood" sign. It was built in 1923 to promote real estate property, in 1945 it was given to the city of Los Angeles. In 1949 the Hollywood Chamber of Commerce began a contract with the City of Los Angeles Parks Department to repair and rebuild the sign. The contract stipulated that "LAND" be removed to spell "Hollywood" and reflect the district, not the "Hollywoodland" housing development.
In the opening sequence, when Cliff crash lands the Gee Bee, Alan Arkin (Peevy), narrowly missed being severely injured when a cable pulling the mockup of the plane along the runway snapped; striking Mr. Arkin behind one of his knees.