Most of the US Air Force personnel are played by British actors. When the Sergeant reports to Major Jeff Cummings early in the film, he incorrectly gives the Major a "British" salute, with the palm facing outward. Thompson returns the salute correctly, with the palm facing inward.
Major Cummings' first visit with Professor Walgate and the search through the woods by the townsmen are presented as being simultaneous, but the visiting shots are presented in daylight while the search shots are presented as nighttime.
Near the end of the film when Maj. Cummings is running up the stairs at the power plant there is a body hanging over the wall but in the previous scene when he is running across the parking lot toward the stairs the body is not there.