Continuity mistake: When Ethan finishes showing Nyah the pictures of the aeroplane crash so she can see what kind of man Ambrose is, she puts out a candle with her hand. Then when they show her from the front, it's lit again, from the side it's out, then lit from the front, AGAIN!
Continuity mistake: In the scene where Nyah is walking up towards Ambrose's house, the wind is playing havoc with Nyah's hair and scarf. Throughout the scene, there are several shots of her where there is no wind, her hair is not moving and the scarf is perfectly placed (most noticeably when she steps off the boat onto the walkway).
Continuity mistake: In the rock climbing scene, just after Hunt does his flying jump, he falls, slides down a smooth rock face and grabs a hold at the last minute to stop him plummeting to his death. When he pulls back up, and over he grabs a hand hold on the smooth surface which wasn't there before. If you know what you are looking for, you will also see that it is a bolt on hold which has been attached to the rock face.
Visible crew/equipment: At the end, when Tom Cruise throws the knife at Dougray Scott's feet, there is a quick succession of shots consisting of the two in a fistfight. In one of the quick shots, as Tom Cruise is debating throwing the knife, then charges instead, there is a distinct black shape at the bottom right side of the screen that belongs to neither Cruise or Scott. The shoulder of a crewman who got a little too close, perhaps?
Factual error: Near the end, Ethan Hunt and Sean Ambrose engage in a high-speed motorcycle chase that culminates with them crashing their motorcycles head-on. Just before the crash, both men leap off their bikes and their bodies collide in mid-air above the crash. However, if Hunt and Ambrose were racing towards each other at 40 mph (a conservative estimate), then the combined force of their bodies colliding would be equivalent to an 80 mph impact, which would pulverize their skeletons and kill both men instantly.
Continuity mistake: The 747 that crashes in the beginning of the movie has a fictitious airline name painted on the fuselage; but the dialogue uses a different name.
Factual error: The portrait of Semana Santa (Eastern) celebrations in Sevilla are absurd. Weird wooden constructions on fire (I guess it refers to Fallas, a celebration from Valencia and Alicante, around 400 miles away, in a tradition in which people burn cheap satirical and arty polystyrene sculptures with the arrival of Spring). Repetitive satanic hymns, fantasy castles, ritual drums, fireplaces and candles everywhere, effigies on sticks on flames, traditional clothes from somewhere in Central America mixed with San Fermín outfits and flutes (from Pamplona, over 600 miles away), frantic dances and women throwing flower petals over the crowd. I only miss some bulls dancing around in flamenco clothes while drinking sangría. The equivalent would be to portray a US festival in which Mickey Mouse rides a horse wearing a scary pumpkin mask while being carried by a leprechaun watching fireworks.
Factual error: The aeroplane at the beginning of the film is a 747-400. You can tell because the wings had winglets when they showed the exterior view. Well, a 747-400 only has a two man cockpit, there is no "sideways flying" flight engineer like in the movie.
Factual error: The car chase between Ethan and Nyah is supposed to take place in Spain involving Spanish cars (plate's colour and the way numbers and letters are represented follows the Spanish code), but a real Spanish plate should have numbers and letters displayed as follows '1234 ABC' or 'AB- 1234-AB'.
Continuity mistake: When Ethan makes the spectacular leap during the rock climbing scene, you see him land vertically, as in he landed in a standing position, clinging to a rock safely, yet when it immediately cuts to another angle, he is already sliding down to the edge.
Continuity mistake: When Nyah and Ethan are in the tub at the mansion, one shot shows Nyah with the heels of her feet up, then it switches to where they're facing the bottom of the tub.
Visible crew/equipment: At one point in the scene where Tom Cruise is escaping with the antivirus, but before he gets on the motorcycle, he jumps and sort of flips and manages to shoot someone while upside down. When he lands, the ground ripples like a waterbed, revealing that it was some sort of pad to cushion his fall.
Visible crew/equipment: During the bike chase at the end of the film, a stunt man in full leathers and crash helmet can be seen on one of the bikes - none of the riders were wearing anything like that.
Continuity mistake: In the first scene Ethan is climbing - he makes a strange jump and he manages to move from one rock to another, but after that tremendous front-hit his t-shirt is perfectly clean...what soap does he use?