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 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)
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.