Continuity mistake: In the scene in which Hugh Marlowe and his fiancée are on the alien ship, speaking with the aliens, his arm is over her shoulder when shown from the front, but down and he is about a foot away from her when shown from behind. The shots alternate back and forth, front and behind, so that the mistake is fairly obvious. (00:37:50)
Visible crew/equipment: During the final attack after Carol falls on the floor in a hallway in the Pentagon there's a shot of a crowd running towards the camera. The woman in the front has the shadow of the boom mike right on her forehead as she comes close to the camera screaming bloody murder. (01:13:25)????
Visible crew/equipment: At "Operation Sky Hook" Dr. Marvin listens back to the tape recording that he was making as the UFO flew over their car and if you look closely the spool of tape on the recorder is at the halfway spot. Earlier as he was making the recording the spool of tape was at the end. (00:05:15 - 00:07:45)????
Deliberate mistake: After the alien ship destroys the bomber, Dr. Marvin picks up the helmet and they all start to run back to the car. In order to save time in repositioning the camera they start out 50 feet behind where they just were in the previous sequence and run back to the exact same spot. (00:57:50)????