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)????
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. (00:54:20)????