Continuity mistake: At sky hook the soldiers pull up in a jeep and jump out carrying M1 carbines. In the next shot when they lay on the ground to fire at the aliens they are armed with M1 Garands.
Continuity mistake: Dr. Marvin tries out his new improved magnetic interference unit and an alien craft is spotted flying around inside of the Belmont lab above their heads. Before the craft takes a dip down at them they're standing on the right of Dr. Marvin's magnetic device, but when we see them again they're standing on the left of his device. (00:50:20)
Continuity mistake: Dr. Marvin walks in as Carol sleeps in their hotel room and then proceeds to call the aliens on his shortwave radio. By the time he walks out of the room to meet with them by the Chesapeake Bay the items on top of his dresser have moved, without anyone going near them. (00:31:10)
Continuity mistake: Carol and Dr. Marvin are locked in the underground bunker at "Operation Sky Hook" as the power goes totally dead. Somehow in total darkness without any power we still hear the sound of the aliens speaking which is strange because if you look at the tape recorder it's not running at all. (00:24:40)