There was to have been a scene in which Clark Gable jumped out of a plane at an altitude of 25,000 feet. The stuntman Jim Unger, who was to double for Clark, passed out at 20,000 feet from lack of oxygen and the shot never got made.
Three scenes show radio operators sending Morse Code. One code key looked like a J-38 single key and two were a two paddle key made by the Vibroplex Company which is still in business. The Vibroplex is also known as a Bug because of the bug logo on the key.