Other mistake: In the pre-credit scenes when the chopper spots the runaway car, Driver guns it (he clenches his jaw, fists and you hear the engine revving and gears changing) but he never catches up with the two cars only a few feet in front of him (which are proceeding at normal speed) for the whole length of the bridge.Giacomo Chizzola
Revealing mistake: While Bishop and Steve McKenna are practicing with various firearms, a slow-motion shot in the film of Steve shooting a .50 caliber rifle shows that, while the sequence depicts him firing "live" rounds, the extracted shell casing is from a "Blank" cartridge (evidenced by the crimped forward portion of the brass casing). (00:34:15)
Plot hole: When Ethan meets the Secretary in the car, he tells him that Hendricks was seen leaving the Kremlin with the nuclear launch device and deduces that he is Cobalt. The Secretary then gives Ethan the flash drive containing his mission, which Ethan reads on the train. Ethan then tells the rest of the team that - according to the mission - IMF believes that Hendricks is Cobalt and was seen leaving the Kremlin with the launch device - hence why he needs to buy the launch codes from Moreau. How could IMF have known about this information to put it on the drive, given that Ethan just told the Secretary in the car?Brad
Audio problem: This scene is repeated multiple times in the movie: usually when the main character enters the "source code" the scene begins by panning over a small pond showing a Canada goose taking flight. However the sound editor makes the mistake of dubbing in a recording of a hen mallard duck.flynn
Factual error: In the scene straight after the opening credits we are taken to Baker Street where construction work is being done. This work is identified by a sign with a logo as being for the underground line. The logo type face was developed by a Mr. Edward Johnston for London Underground from 1913 but the distinctive typeface used in the film was not in place until 1919. This is obviously long after the 1891 setting of the film.