Other mistake: When Polly notices the reflection of Joe's airplane marking on the water, the code "hllod" gives "Polly." That's impossible. To get "polly" from "hllod," a person would have to rotate the word 180 degrees, not view it as a mirror reflection.
Factual error: At the very end, Polly Perkins takes a spectacular picture, using the very last shot on her only roll of film. When Sky Captain tells her she left the lens cap on, she is mortified. But she would certainly know that on her Argus 35mm camera, all she had to do was remove the lens cap and retake the shot. Unlike modern idiot-proof cameras, hers has no mechanism to prevent double-exposures.
More trivia for Sky Captain and the World of Tomorrow
Question: When the Hindenburg III docks with the Empire State Building, the newspaper shows early October 1939. Is there any clue as to what went differently in history concerning WWII?
Answer: None.
Rlvlk