Character mistake: In the scenes in San Diego, all the scenes outside the sub are taking place during daylight hours. Immediately after the crewman relays the message about the mysterious telegraph transmission, the scene shifts to the sub. The commander asks what time it is in Melbourne and is told it is 1500 hours (3PM). But if it were that time in Melbourne, it would be 10PM in San Diego, and thus not during daylight hours. (01:33:30 - 01:38:05)
Character mistake: The pilot says to his wife that the flying saucer was cigar-shaped. The actual shape was more like two dishes attached together. (00:04:45 - 00:12:20)