Revealing mistake: When Benji imagines putting on a mask of an agent he plans to impersonate, when the camera pans around to first show the mirror, the mirror Benji's hands are further up on his face than the reflection, and the mirror Benji's hands move down his face slightly before the reflection starts to move them. Also, the mole that Ethan has on his left cheek isn't reversed in the mirror image. The "mirror" was actually a hole in the wall between two identical sets (one mirrored), with Simon Pegg and a Tom Cruise double in the foreground, and the mask actor and Tom Cruise in the background "mirror" set. (00:57:20)
Factual error: Breaking through the power plant glass roof, the glass is wire reinforced and would not break in the way shown. (01:01:46)
Continuity mistake: After reviving Ethan after escaping from the water tank, IIsa's bra strap is visible under her tank top. When she changes later, the bra disappears. (01:10:00)
Continuity mistake: During the bike chase scene, Ethan chases the last rider who is trying to shoot IIsa. He follows a right bend to catch and get in the inside of this rider. Ethan then knocks him from the inside of the bend. As he is on the inside of the bend, he would be knocking the rider to the left. However, in the next shot Ethan has knocked him off on a straight road with the bike and biker now falling to the right, which would be impossible from the previous shot, with both rider and bike falling towards an embankment. In last segment the scene changes back to Ethan exiting the bend with the rider's bike travelling now in the opposite direction along the ground towards the edge of the road, before exploding when hitting the barrier. (01:16:00 - 01:17:00)
Factual error: Towards the end of the film, Solomon is trapped in a small Plexiglas box and fires his gun into the bulletproof sides numerous times, but the bullets don't ricochet or get embedded in the glass.
Continuity mistake: Ilsa walks across Westminster Bridge, but in the very next shot after she has crossed the bridge she is walking towards it - she should be walking away from it.
Continuity mistake: The timer towards the end doesn't match up with the elapsed time, despite being a continuous sequence. It runs fast soon after it's started, then in the final seconds the audible beeps (one per second) are mismatched with the count.
Factual error: When the gas is turned on for the box, the red handle was moved to a right angle to the pipe which is standard for the off position.
Continuity mistake: When Ethan and the girl are sliding down the rope at the opera, in one shot, as it should be, her dress is up around her neck - that is all we see - and in another shot, the dress is down around her ankles, which it shouldn't be.
Suggested correction: The top of her dress is also fluttery and could have created the illusion that her dress is up around her neck.
That's not the top of her dress we see. The top is fitted over just one shoulder, there's not enough material to cover up her shoulders and neck like it does. It's the bottom of her dress.
Plot hole: Before the IMF team can exchange the yellow cards for the access control, they first need to know the data format/file type in which the access rights (retina, gait, fingerprints...) are stored. Otherwise, the computer will not recognize the data on the card, and display an error to the maintenance personnel. In order to figure this out, they would need to steal first some of these yellow cards and analyze the data on them, before they can fake a card which will be accepted by the computer.
Factual error: During the car/bike chase the air bags for the car should have gone off many times, most notably when the car hits the truck with the bike rider on the bonnet.
Suggested correction: The collision mentioned above was an impact at the C-pillar of the BMW. As someone involved in several traffic accidents, I know airbags are not infallible. The only airbag that MAY have been activated would be the side curtain airbag and only if the impact was near the sensor. Normally, side curtain airbags activate only in rollovers or direct T-bones.
Deliberate mistake: If the files on the hard drive are encrypted, as stated, they would also be locked against being deleted by a command, and Atlee would not be able to use a phone in close proximity to issue the delete command. He would need a massively powerful magnet or EMP to clear the drive.
Continuity mistake: In the Vienna subway, Benji tries the glasses on and a woman and an old man approach from behind. A shot later they're suddenly already several meters ahead.
Continuity mistake: When Benji receives the opera tickets he opens the brochure completely. When the shot changes the left page is not fully extended.
Continuity mistake: In the basement, the last guy Ilsa and Ethan knock down lies sideways. A shot later he is lying face down.
Factual error: They are meant to be taking off from Belarus in the opening scene. However when they fly over the roads the traffic is driving on the left hand side of the road.
