Continuity mistake: When Ethan wakes up in the hospital he realises he's handcuffed to the bed. In the closeup of his right hand, the handcuff is around his wrist with its single metal bar facing out and the double bar facing Ethan, but when the nurse moves his gurney the handcuff is around his right wrist the opposite way, with the double bars facing out. Quite impossible for this to occur. (00:31:50)
Continuity mistake: When Ethan gets instructions on the screen in the payphone there is a countdown on a screen visible, a split second later when the camera shows the phone from a distance that screen has gone and the payphone is 'closed' again. (00:19:10)
Other mistake: When Benji kills Wistrum, the bullet hits him square in the back, even though Benji shot him from the side.
Continuity mistake: As Ian chases the bad guy and the sandstorm approaches, he enters a covered area just as the shadow of the storm (moving much faster than he is) reaches him. When he exits the covered area, 5 seconds later, the shadow remains *just* overtaking him, while it should be easily 10 meters past him by then. (01:16:43)
Continuity mistake: When Ethan disguised as a Russian officer passes the security scan at the Kremlin, he goes without the controller giving him back his fake ID card. In the next shot showing him, Ethan puts it back in his pocket.
Continuity mistake: Ethan is walking down the steps of the airplane and the car drives by. He is then one step back up. (01:31:15)
Factual error: When the four main characters get together at the end of the movie and meet Luther, it is said to be in Seattle. Benji says all the people around them were almost vaporized. The nuke landed in San Francisco and if it had detonated, it wouldn't have affected Seattle so drastically.
Other mistake: When Ethan drives a car off the edge of the parking ramp the car falls 100 meters to the bottom pointing nose down the whole way and hitting nose first allowing Ethan to be saved by its air bag. The car's angular momentum makes this impossible - the car would have tumbled back over front.
Chosen answer: The missile launches from a Russian silo. They want to stop them preventing the launch locally.