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)
Continuity mistake: When Cobalt piggybacks IMF's frequency, he says "Team leader, awaiting your go sign. Standing by to detonate." When Sidorov plays the recording back to Ethan in the hospital, the order has changed to "Awaiting your go sign, team leader. Standing by to detonate." (00:31:25)
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.
Continuity mistake: This is at the fancy car park in India. Hendrick has just jumped off the platform. The briefcase as well as his body move in subsequent shots. Note the lines in the concrete floor.
Other mistake: During the car chase scene in Dubai, Ethan pushes the clutch several times (visible in the leg-room shots). The car, however, has an automatic transmission.
Continuity mistake: In the prison break scene, when Benji opens the second prison cell, the computer shows that he is opening the second cell, but the third cell actually opens.
Chosen answer: The code Jane got from Brij Nath (the Indian billionaire) was not a nuclear launch code, it was an access code for an old Russian satellite Nath owned, which Hendricks was using to launch the missile. Once Benji had the codes, he used the satellite to locate where Hendricks was also accessing the satellite from the TV station.
Sierra1 ★