In the movie when they show all of the headlines from newspapers around the globe, you can see Godzilla's outline on the Tokyo newspaper. In one of the newspaper shots you can see an "Iron Eagle", which defines the Nazi regime to be in power in Germany, although there is no sign of a preparation for war.
An emergency distress call is transmitted to Sky Captain by means of visible radio waves, coming from a radio tower that is unrealistically large and out of proportion in relation to the size of the Earth. This is a reference to RKO Radio Pictures Inc., whose logo features an abnormally large radio tower sitting on top of the Earth, emitting visible radio waves.
While the project was still in early development, Kerry Conran originally wanted to produce it as if it were a lost serial from the 1930s, with the film featuring unknown actors, shot in black and white, and divided into chapters each ending with a cliffhanger. All of these ideas were subsequently abandoned in an attempt to gain bigger box office appeal.
In preparation for her role, Angelina Jolie met with and interviewed dozens of British WWII veterans and pilots in order to adapt the proper mannerisms of her character. She also tweaked the script by adding bits of slang that were used during the era.
As Sky Captain and Polly fly submerged with "The Amphibious Squadron," they "overfly" a sunken steamer named "Venture." It's the ship used to bring King Kong to New York. It even includes on its deck a cage large enough to confine Kong; implying perhaps that this is the original Skull Island.
When Polly is on the phone to her editor, reporting the advance of the giant robots, her line is "They're crossing Sixth Avenue... Fifth Avenue... they're a hundred yards away...". This is a direct lift from Ray Collins's lines in Orson Welles's "The War of the Worlds" broadcast of 1938 as Collins plays a reporter on the roof of "the Broadcast Building" reporting the advance of the Martian tripods.
The paint job on Joe Sullivan's plane is that of the "Flying Tigers", a group of American fighter pilots (supposedly) paid by the Chinese government to fight the Japanese in Burma. The "Tigers" themselves got the idea from RAF planes based in Africa in the early part of WW II. Joe briefly mentioned flying for them while arguing with Polly Perkins about his sabotaged plane. The Flying Tigers were revealed in 1991 to have been a "black" operation of the US Armed Forces under direct authorization by President Franklin D. Roosevelt.
The entire movie was shot against blue screen, with everything except the main characters computer generated. This was one of several movies to take that approach (although which was first is debatable), including: Immortal (2004), Casshern (2004), and Sin City (2005), the last of which shot on High-Definition digital cameras, like this movie. Because of the film being totally shot against blue screen rather than via orthodox locations and sets, filming was completed in just 29 days. Normally with sets and locations, filming could have taken the best part of a year to finish.
Early drafts of the script called for Gwyneth Paltrow's character to be covering the 1938 premiere of Snow White and the Seven Dwarfs (1937) at Radio City Music Hall. The plot was later changed so that Polly Perkins meets with a scientist at the theatre, with the film (Snow White) playing in the background. However, a copyright agreement could not be settled with Disney, so the film was changed to The Wizard of Oz (1939).
In addition to the hologram towards the end of the film, the old photographs of Totenkopf are actually of Laurence Olivier. They are modified to add the Unit Eleven logo, as well as to replace Vivien Leigh with Bai Ling.
The devices near the end of the movie that zap the unsuspecting scientist are actual devices called Tesla Coils. Although not used for that purpose, they do arc electicity over the air in a similar fashion.
To increase flexibility with the film's editing process, Kerry Conran shot each of the dozens of extras (who weren't physically interacting with the main characters) individually on the blue screen, so that he could manipulate them in the final shot to his own liking without having to re-shoot the entire scene.
During the first robot scene, a movie theater is seen called the Densmore Theater. This is named after Densmore Street in Van Nuys, California, which is where the World of Tomorrow post-production studio was located.
When Polly and Sky Captain investigate Jennings's ransacked lab, they discover a live, miniature elephant in a glass cage. This echoes a similar scene in Michael Crichton's novel Jurassic Park which describes John Hammond's proud accomplishment of a dwarf elephant, created by his scientists. This may also be an homage to the 1940 film, "Dr. Cyclops", which featured a mad scientist creating miniature animals.
Much of the production design was inspired by artists from the 1930s, such as Hugh Ferriss, Raymond Loewy, and Norman Bel Geddes. Renderings of New York City by Ferriss were models for the art deco New York City seen in the film, and the Flying Fortress was designed after drawings of ocean liners imagined by Bel Geddes (note the ship-like qualities of the Fortress in the film). Many other objects and settings used the stream-line designs of Loewy's works.
Kerry Conran never went to New York City while making this film, and had never previously been there. He digitally recreated the entire city by referring to old photographs, some of which are even inserted into the digital environments as backdrops. Originally, the plan was to have every New York City backdrop be a colorized photograph, and that idea remained in effect until mid-production, until it was decided that 3D renderings of the city would allow the camera more of an opportunity to move around.
Sky Captain flies a late-model P-40, the six gun version of the P-40N. However, his has a few "Hollywoodifications": - The rear decking behind the pilot's seat, and the fuselage fuel tank under it, were removed in order to add a second seat (for Polly). This was actually done to some real P-40s for flight instruction. - The pop-open bays for the cable launcher and magnet bombs are right in the middle of the centerline fuel tank (which fills the interior of the wing between the main wheel wells). - The small underwater engines under the horizontal stabilizers would retract right into the tail wheel gear well, and into each other. - When going into underwater mode, the ostensibly solid-metal propeller blades collapse down into the prop spinner, and into a different section of space-time. The real plane's prop spinner is a shell that goes around the collars and gearing of the prop hub assembly. - Roughly 5000 horsepower appears to have been added to the 1200hp Allison engine.
The logo for the Flying Legion is a winged lion with a banner reading "Ille Caelum Fremitus", which is Latin for "Yon roaring of the skies". The Latin form "caelum" is an unusual, poetic contraction of "caelorum".
The film originally started out as a six-minute reel put together by Kerry Conran of CGI robots trampling through New York City, The World of Tomorrow (2005). Producer Jon Avnet came across the reel and was deeply impressed, so he approached Conran with the idea of turning it into a full-length production.
While set in a "real" New York City, the history is obviously changed. The Wizard of Oz (1939) and Wuthering Heights (1939) references put the year at 1939. Despite being 1939, there is no sign of Germany preparing for war. There is also no sign that America is in the grips of an economic depression. All-in-all, not only is the technology "fantasized", but the entire history is idealized as well.
The names of people who worked on the film appear several times. On the first issue of The Chronicle shown in the film that reports the docking of the Hindenburg III at the Empire State Building, multiple headlines contain references to Kerry Conran and brother Kevin Conran (headline "Conran Ministry Force Deal"), Darin Hollings ("Dr. Hollings Speaks"), Omar McClinton ("McClinton seeks license to halt sanctions"), Brian LeachZack Petroc ("Leach and Petroc Break Over Budget"), and Stephen Lawes ("Lawes Held Ready to Aid U.S. Peace Action"). In the issue of The Chronicle with the headline "Giant Machines Steal Refineries," the article is shown to be written by Marsha Oglesby, one of the film's executive producers. Although dim lighting makes it practically invisible in the film, there is a list next to the giant wall map in the Flying Legion base, which contains the last names of several crew members.
There actually were a few sets built. The only full set constructed was Polly's office, used during the scene where she is confronted by Editor Paley before leaving to meet Dr. Jennings. Dr. Jennings' lab contained many real tables and props, with bluescreen backgrounds, and his office was almost entirely real with the exception of the exterior seen through the window which the Mysterious Woman uses to escape.
Sky Captain's revolver is an Enfield No. 2 Mk I chambered for .380/200 (aka .38 S&W). The automatic he periodically uses (the one which magically transforms back into the revolver when he loses it on the log bridge) is a nickeled M1911 .45 (most likely a Colt).
The interior of Radio City Music Hall is actually not computer generated; rather, the background is comprised of digital photographs taken by Darin Hollings and Eric Adkins, merged together to create a panorama backdrop. The same was done for the lobby of The Chronicle building, which was actually a combination of multiple different building interiors edited together.
When they come across an abandoned mine, on the top of the mountain there is a sphere-shaped figure with a tall prism next to it. These are the Trylon and Perisphere, which were famous icons in the 1939 New York World's fair.
Polly's article reporting the disappearance of Dr. Vargas reads: "NEW YORK-German Scientist and mechanical engineer Professor Jorge Vargas mysteriously vanished after arriving in New York aboard the Hindenburg III. Prof. Vargas was scheduled to lecture at the American assembly with two other scientists. This marks the third disappearance in as many months of important figures in the science community. Demands have been made for a resolution to this problem. Prof. Vargas was to deliver a paper on efforts in Norway and South Africa."
The "hit list" shown near the beginning of the film shows the names of the Unit Eleven scientists to be: Dr. Otto von Funderburg, Dr. Matthias Hargett, Dr. Arler Kessler, Dr. Herbert Braun, Dr. S.L. Aufkäuser, Dr. Jorge Vargas, and Dr. Walter Jennings.
Totenkopf's name, derived from the German for "Death's Head," and his machinations were based on Hitler's infamous SS-Totenkopfverbände, who ran Nazi Germany's extermination and concentration camps. The SS unit was known for creating new ways of making the camps more efficient and deadly. They also assisted the camps' doctors who experimented on prisoners in much the same way the diseased man in Shangri-la is afflicted.
A moment after the encounter with the hologram of the face of Dr. Totenkopf (Laurence Olivier), Joe, wondering if the door is still booby-trapped, asks Dex: "Is it safe?" This appears to be a reference to the line "Is it safe?" asked repeatedly by Dr. Szell, the villain of the movie "Marathon Man." Szell was played by Laurence Olivier.
The Giant Robots that attack New York are a homage to the Max Fleischer "Superman" cartoons of the 1930's and 40's. The robots are taken from the episode "The Mechanical Monsters". In both instances, the robots are remote controlled by radio signals.
The film was originally slated to be released on 25 June 2004. However, it was moved to September 17th so as not to compete with the summer blockbuster Spider-Man 2 (2004) and to give more time for the production staff to fine-tune the finished product.
When Sky Captain and Polly first arrive at the uncharted island, and Sky Captain floats the plane, exits, and stands on the wing assessing their situation, you can clearly see the number on the side of the plane as "h11od". When viewed upside down spells the name "Polly". Since in that era the call marking on a plane became a personalization of the pilot, this alludes to who really was meaningful to Joseph Sullivan: Polly Perkins.
The trivia item below may give away important plot points.
After the image of Dr. Totenkopf (played by Sir Laurence Olivier) is deactivated, it is discovered that the real Totenkopf has been dead for quite some time. Joe comments that "We've been chasing a ghost." The irony is that Olivier himself had been dead for over 15 years before the film was created; Kerry Conran achieved this by using CGI-manipulated archive footage of Olivier.