Plot hole: After being denied permission to contact the aliens by himself, Dr. Marvin returns to his hotel and calls them up on the radio anyway and arranges to meet, despite not being allowed to leave the hotel. His wife says she overheard him say he's under orders not to leave and begs him to call someone instead: "Call Huglin". She shouldn't know who Huglin is because Huglin was only assigned to guard them as Marvin was being denied permission to contact the aliens.

Factual error: The aliens request a meeting with Dr. Marvin on the shores of the Chesapeake Bay, near Washington DC. However, the shot of him driving along the shore line shows mountains in the background, which don't exist in Eastern Maryland.

Visible crew/equipment: Dr. Marvin decides to try out his new improved magnetic interference unit on a real alien spaceship that shows up outside the Belmont lab. As the truck with the device on it pulls up you can see the reflection of the crew in its door.

Deliberate "mistake": The aliens fire on a bell tower with a clock on it. In the next shot a different building blows up.

Continuity: 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.

Deliberate "mistake": Two trucks with magnetic interference units on them are shot at by the aliens and the exact same sequence is used again three shots later as they shoot at them again.

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.

Continuity: The UFO flies over the Marvin's car as they approach "Operation Sky Hook", and Dr. Marvin tells Carol to pull over. She immediately turns the steering wheel to the left but in the next shot she's steering straight ahead.

Visible crew/equipment: The general gets a phone call just as Carol gets ready to leave his office at the Pentagon and he tells her, "You better get down to the shelter". As he says this the camera zooms in and it's shadow can be seen on his desk.

Continuity: A saucer crashes threw the main window of a train station and the clock reads 11:10. Two shots later we see the clock on the other side of the building and it reads 10:43.

Deliberate "mistake": As the saucer lands on the White House lawn the aliens walk out and fire on some soldiers, killing them. A few shots later we see them walking backwards into their spaceship as the film is obviously run backwards.

Audio problem: Dr. Marvin watches the magnetic interference unit take down an alien spaceship and says, "…saucer hit and down in the Potomac". If you look closely his lips do not match what we hear.

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.

Visible crew/equipment: Watching the alien spaceship that lands outside the Belmont lab they all get out of the car and Carol says, "I'll get them from Russ". If you look closely as she opens her door, the reflection of the crew can be seen in the passenger side vent window.

Continuity: Before Dr. Marvin removes the helmet from the dead alien, Maj. Huglin is holding his rifle in his right hand. In the next shot he's using his right hand to remove the helmet. Then in the shot after that he's not touching the helmet at all.

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.

Continuity: We see the alien ship before it destroys the Pacific Paint Company with what looks like a beautiful cloud filled sunset behind it. In the next shot as the building blows up the sky is cloudless.

Deliberate "mistake": As the alien spaceship attacks a bomber we see it superimposed through the windshield. The pilots never react because they're not actually seeing it and are poorly directed.

Visible crew/equipment: When seen up close the aliens helmets have no openings. When the alien spaceship takes off outside the Belmont lab one of them is left inside. As he walks out the reflection of the window on the front of his helmet and the person in side can be seen in the sunlight.

Continuity: As Prof. Kanter is incinerated by the alien's beam we can see the shadows cast by the leaves of the trees move before our eyes between shots.