Revealing mistake: When the huge alien ship settles over the White House there is an exterior wideshot of the grounds. At the bottom of this shot it's funny how there are many tourists - adults and children, just milling around in front of the gate and across the street with a van driving along between the two sides, and not one has any sort of reaction to the alien ship. This real shot of the White House (some shots had smaller-scale models) had the CG ship edited in during post production. (Visible on fullscreen DVD.)
Revealing mistake: When Jeff Goldblum is throwing a tantrum in the hangar housing the captured alien craft, he knocks over several plastic garbage cans, one of which is clearly labelled "Art Dept" - kind of odd for a top secret underground government military research facility. (01:35:15)
Revealing mistake: The following take place in F/A-18s. After Jimmy says, "I got you covered, big daddy," there is a close-up of his gloved hand as his thumb presses the launch button. Later, when President Whitmore fires his last missile (with negative impact) there is a close-up as his thumb presses the launch button, and then a minute later there is a close-up of Russell's hand as he presses the launch button (resulting in launch failure). The last two close-ups are the very same shot as shown earlier, only the last two shots are flipped the other way. (00:57:25 - 02:04:00)
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.
Revealing mistake: When Will Smith and the other jets are flying into the ship and are firing their missiles there is a cloud in the background that doesn't move. You can tell it's a background set piece. (00:58:20)
Revealing mistake: When Marty is stuck in traffic in his car, trying to get hold of his therapist, there is an overhead shot just before this one showing traffic with a few taxis. This traffic shot is flipped - note the steering wheels on the right side of the cars. This particular shot is shown again, but not flipped, just after the Empire State Building blows up. (00:44:00 - 00:47:10)
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 comes up along the entire bottom edge of the screen. This is only visible on fullscreen DVD. (01:08:10)
Suggested correction: That is another jet guarding Air Force One.
Revealing mistake: In the scene where Jasmine, her son and her dog are trying to escape by jumping out of a cab and running, she turns and looks toward the explosion. You can see that she is carrying a very big, very stuffed mannequin. (00:51:30)
Revealing mistake: When the aliens attack LA, there is a shot of red and silver cars. The same cars fall three times onto other cars, from three different angles. (00:51:00)
Revealing mistake: When the Welcome Wagon is being shot down you can see an explosion starting inside the last helicopter before it is even being hit.