Continuity mistake: When President Whitmore and the rest get to Area 51, you see David Levinson in the background. Right before they go through the doors, he has a sunglasses clip over his glasses. As they start walking down the ramp, they are still on, but right after the glass doors open, you can see for a second or two the clip is off the glasses. Then when they go for a close up of Levinson, you can see him take the clip off. (01:14:55)
Revealing mistake: At Area 51, when the president's entourage fire their guns at the alien, the stunt wires attached to its upper body are visible, pulling the alien backwards. These stunt wires have nothing to do with Dr. Okun's medical equipment.
Continuity mistake: When Russell boards the F/A-18 and when he is airborne - such as when he salutes Major Mitchell (who is back at command center), he wears his Hawaiian style short-sleeve shirt and is gloveless. After he says, "Eagle 20, Fox 2," in the close-up as he presses the launch button (resulting in launch failure), the arm shown wears both a green jumpsuit and gloves, neither of which Russell actually wears.
Visible crew/equipment: When the President stands by "the big tamale" he asks Dr. Okun if he can tell them anything useful about them. When Okun rushes up the ramp as he passes Nimzicki, the actor's mark is visible on the ramp, directly in front of the Secretary of Defense. (Only visible on fullscreen DVD.)
Visible crew/equipment: After General Grey shows the nuclear missile and launch mechanism to Steven and David, when Connie asks, "Why you?", in the next shot just as a woman in a white lab coat passes David, his yellow actor's mark is visible on the floor at his feet. (Only visible on fullscreen DVD.)
Continuity mistake: When the alien aircraft settles over New York, there is a taxi cab driver that stops to look, and the truck behind actually hits it twice. Also, there is a parked yellow school bus which the front half of the taxi passes in the wideshot, but in the close-up, when the driver gets out, the taxi is actually much farther back, the bus is gone, just take note of the gate in the background. (00:22:25)
Continuity mistake: At the decimated MCAS El Toro, when the First Lady asks Jasmine what she does for a living, the First Lady holds the bowl out with her left hand in the shot facing Jasmine, but in her right hand in the shots facing facing her. The direction of the bowl's handle also changes.
Revealing mistake: In the exterior shot of Air Force One and its accompanying jets in the air, just before the shot of David getting nauseous aboard Air Force One, something suddenly appears along the entire bottom of the screen. Whatever it is, it shouldn't be there. (Visible on fullscreen DVD.)
Continuity mistake: In the interior shot, when Jasmine tries to explain why she doesn't want Steven to leave she pulls open the white curtains, to view the alien ship through the window (the window closest to the door), and as Steven walks out the front door she stands by that open window. Then when it cuts to the exterior shot, in an instant that window's brown venetian blinds are now down and the white curtains are drawn closed, as Steven walks down the lawn.
Visible crew/equipment: When Russell lands his crop-dusting plane and Miguel rides up alongside on his motorbike. The equipment used to help stop the motorbike, at the right position for the close-up, is visible on the ground - but it's gone in the wideshot. (Only visible on fullscreen DVD.)