Continuity mistake: Ethan and Grace are in a car chase, trying to get away from Paris. The Fiat Ethan and Grace are driving makes a left turn, and you see a dark blue car parked at the corner. Paris is driving the armored vehicle and makes the same turn, but the dark blue car has disappeared. (01:07:36)
Factual error: Gabriel kills the engineer and sets the train to full speed, then locks the control room. Without the engine being resupplied with coal it would lose power and stop before too long, never getting as far as the bridge.
Suggested correction: It is known for firemen to fill the loco up to allow it to run for 15-20 minutes without new coal. However, it could not run that long at that speed without the boiler being refilled with water, so the boiler would have exploded well before the fire reduced.
Factual error: Ethan decouples a moving train, moving the chain link by hand. Impossible as there would be massive tension on it.
Factual error: The Orient Express is not powered with steam locomotives by any of the respective state railways. All of them are diesel or electric.
Plot hole: Benji puts his car into automatic mode, which operates partly through satnav. Surely, this would be monitored by The Entity, who has predicted every other action up to that point. The same car is used at the end of the film, but if The Entity hasn't noticed it by then, it's not as powerful as they think it is.
Other mistake: At first, Ethan tries to board the train by waiting until it slows for a sharp bend. Thanks to The Entity, the train is going pretty much full speed throughout, but doesn't derail or tip at the lower speed sections. In fact, the diners are all blissfully unaware that this is, in effect, a runaway train as they consume their canapés and fois gras, with soft music playing in the background.
Factual error: The car chase in Rome is not possible as depicted: cars are supposed to turn from one street into the connecting one, but in fact, these are miles apart. This happens in multiple instances.
Continuity mistake: During the Venice scenes, Ethan's hair length is always the same, except for scene number 1 where he and the team are on a boat arriving in Venice, and scene number 3 where he and Ilsa are on a balcony. In both these scenes, his hair is very short.
Continuity mistake: When being arrested after the car chase, Hunt and Grace are told to put on the handcuffs. They have their hands up, and neither is holding the cuffs. Then, fired upon, suddenly they are cuffed to each other. Even if explained as a sleight of hand out of shot, from a plot point of view it makes no sense for either of them to cuff themselves to the other at this point. Hunt is trying to save Grace, which makes it harder to do so, and Grace is trying to escape from him, not anchor herself.
Continuity mistake: During Paris and Gabriel's fight in the train, the dead guy behind has his eyes open all the time except for a brief shot where they are closed. A shot later they're open again.
Continuity mistake: When the submarine is hit, the centre is blown into a million pieces. In the next shot, the submarine floats gently to the sea floor untouched. Then it semi-crumbles as it lands.
Continuity mistake: When Grace crashes with the Italian police car, the door is opening up on the top because it was dented. When she puts it in reverse, the door is back in a normal state.
Factual error: When Ethan crashes into the train carriage, he is able to move about, but in reality, he would have been pulled straight out by the parachute and the speed of the train.
Other mistake: Grace crawls across the coal car of the train, and there are several times when she is lying completely prone. In the next scene, there's not a single smudge on her face, hands or clothes.
Revealing mistake: While inside the tunnel in Rome, before the yellow Fiat makes a U-turn multiple skid marks from previous takes are visible. Though one might pressume that the marks were already there, they are at the same spot and have the same pattern as the skid marks that the cars make seconds later.
Continuity mistake: In the desert, when Ilsa is shooting with her eye patch on, a strand of hair on her forehead suddenly disappears between shots.
Continuity mistake: On the roof of the train, Hunt is on top of Gabriel, with a blade right next to his neck. Gabriel says "I know what the key opens," and right then the blade is either touching his skin or inches away, depending on the shot.
Other mistake: Ethan (in disguise) throws some gas grenades in the office where the security heads are meeting - there's a massive explosion. Bright green gas fills the room... And everyone working on the typewriters in the room below completely ignores this, despite having a clear view into the glass window/wall of the office above. Even after a couple of minutes of Ethan and Kittridge talking, the phone rings with someone checking on them, rather than security busting in the door immediately.
Suggested correction: The three explosions aren't especially loud. The sound would likely easily be deadened by the walls and windows. The resulting powder (not gas) that's released is only present for a few seconds before dissipating. Since everyone in the typing pool is so focused on their work, it's quite possible it went unnoticed.
