The villains use nitrous oxide to knock out (not kill) the people on the plane. However, Sean tells his sidekick to disconnect the "NO2 tank", both on-screen and in the closed-captioning. However, nitrous oxide is "N2O". "NO2" is Nitrogen Dioxide, a poisonous, smelly gas that would be immediate noticeable, and would kill the passengers, not quietly knock them out.
In the opening sequence, the pilot reports a partial cabin depressurization and identifies the aircraft as "Trans-Pac 227 747 Heavy". In reality a 747 is, by definition, designated "heavy" and the proper designation would be 'Trans-Pac 227 Heavy'. The "heavy" designation is used to indicate aircraft over 255,000 lbs.
When Ethan comes out of the room where he destroyed the chimera in the Petri dishes, and takes the protective mask off, the top section of his hair is obviously clipped back, but wasn't clipped back earlier, or in the next shot.
When we are shown the satellite positioning itself over Australia ready to home in on Nyah, there are no clouds at all over Sydney. However, in the next shot (taken from the ground), the sky is littered with them.
During the "morning after" when Nyah and Hunt are talking in bed, Ethan leans into her and is practically nose to nose with her and in the next shot is propped up on his arm almost 7 or 8 inches from her, then, in the next shot, they are close again.
While much is made of the 40 seconds available to get Hunt into the Biocyte building and get the cable out again a NATURAL LIGHT SHAFT MANUAL-OVERRIDE alarms systems safety notice appears on the computer screen Luther is looking at. The notice declares: In accordance with city safety code 24395 if the light shaft aperture malfunctions and opens outside of daylight hours, after a period of 20 seconds has elapsed the state emergency services will be alerted.
When Nyah walks away from Sean at the races (after taking the envelope) she swings her arms and has not got the envelope under it, but in the next shot you see her drop it down to her hand after Sean says "Hold on."
After Nyah pick-pockets Ambrose, she places the envelope with the memory card in between her side and arm, and turns to walk away. When she begins to walk away, her arms are spread and no envelope can be seen, but then it closes up on her dropping the envelope into her hand, even though the space in between would have already allowed it to drop.
When Ethan is escaping from the island, he shoots out the tire on the white Ford, causing the hubcap to come off. However, when the driver is swerving and the car flips, you can see that the tire is fully inflated and the hubcap is in place.
After the alarm goes off in the Biocyte building when Ethan detonates the bomb, the real guards who respond to the alarm are shown to be carrying submachine guns. However, when they start a firefight with Ambrose's men, they are only firing pistols.
When Ethan uses the tracking unit to locate Nyah in Sean's villa right on the waterfront of Sydney Harbour, the coordinates on screen are given as 33°52'48"S 151°13'10"E. This puts the house in the middle of the nightlife suburb Darlinghurst, nowhere near the harbour.
The Spanish popular feast Fallas, where wooden figures are burned in the streets, is not celebrated in Seville, as is shown in the movie, but in Valencia. Anyway, the figures never represent saints, but celebrities from politics, sports, society life, etc.
The plane in the opening scene crashes in the Rocky Mountains. However, a plane flying direct from Sydney to Atlanta does not ever pass over the Rocky Mountains. Rather, it passes over central Mexico on the way to Atlanta due to the great circle route that airliners must take.
While red blood cells don't have a nucleus, they can still be infected by viruses, causing haemolysis, which can be fatal. However, *not* by an influenza-based virus; influenza viruses can only attach to surface receptors causing clumping, or haemagglutination.
Ambrose forces the CEO to sell all of his stock to buy options in the company. CEOs of public corporations are not allowed to liquidate a single share without first filing with with the appropriate governmental agency (SEC in the US).
The distance between Sydney and Atlanta is just under 9,300 miles. Although it is possible for a 747-400 (the model of the plane that crashes into the Rockies carrying Dr. Nekhorvich) to fly that far non-stop, it can only be done so with no passengers or freight on board. A fully-loaded 747-400 as depicted in the movie could not fly that distance non-stop without fuel stopovers.
During the big chase sequence, when Ethan Hunt shoots the windshield of Sean Ambrose's motorbike, the angle of the bullet might be sufficient to hit Sean Ambrose, but it also might be sufficiently deflected by the windshield.
In the car chase between Ethan and Nyah, Ethan makes an obvious point of trying to fasten his seat belt (though not succeeding), and the belt is off and on again numerous times throughout the chase. Ethan never successfully put on his seat belt and it only got as far as his shoulder because it locked. Thus, it appears and disappears as though it was never completely done up.
At the start of the movie, Dr. Nekhorvich tells "Dimitri" that he has to be in Atlanta within 20 hours of exposure. Even if it were possible for him to inject himself, get to the airport and then on a plane, with a 15 hour flight from Sydney to LA, and then from LA to Atlanta on a commercial airliner, he wouldn't have made it in time.
From his RT skills, it would have been noticeable very early on to the 747 crew that Sean was an impostor. At cruise, altitude should be reported as Flight Level not height in feet i.e descending to FL160 rather than altitude "one six thousand". He should also not have autonomously made an altitude change without either formally declaring an emergency or requesting descent clearance.
Most of the cars that were smashed or involved in accidents were already damaged before filming, and had been patched up to disguise this fact. This left the front or rear of some vehicles noticeably short or unproportioned.
When Nyah walks out of the jail in Seville before heading to Sydney, she is seen in reflection in Ethan's sunglasses. But the image is not reversed. Note her handbag is on her right side both in the unreflected and reflected images.
When Ambrose receives the final kick to the head on the beach, his head lands against the rock facing the right. When Hunt crawls over to him, preparing to punch him again, Ambrose's head is facing to the left. In the following shot, it's facing the right again.
When Ambrose (who is disguised as Ethan) talks to Nyah outside Ambrose's home at night, he is wearing a beanie. When Nyah heads back inside and Ambrose takes off the mask to reveal himself, and the beanie has disappeared.
At the end of the motorcycle chase seen, both Hunt and Ambrose jump from their crashing bikes and collide with each other falling several meters down to the beach. At the velocity the bikes were traveling (based upon the audible rpm and gear shifts, and action of the bikes after colliding), both Hunt and Ambrose would have been subject to the physical effects of a 60 mph car crash, not to mention the fall to the beach below. It is more likely they would have been killed.
Toward the end, when Ethan sees guards emerging from the facility he shoots at some barrels, which explode. When the camera zooms in on the barrels just before they explode, they are clearly marked Biohazard, not Flammable, and by their very nature would never be flammable.
Toward the end of the movie, the amount of ransom asked was 30 million pounds. The amount shown on the computer screen during the bank transfer is $30,000,000 (dollars instead of pounds). Also, banks generally use abbreviations (GBP, USD) instead of symbols for international transactions.
When Ethan Hunt destroys the Chimera virus in the lab, the computer confirms "Organisms exterminated"; while viruses may not be considered by some to be "organisms," experts in the field often refer to them as such. In any case, the lab might be using software that isn't specific to viruses.
Nyah is infected late at night (11 P.M. when the generators go off), Ethan has 20 hours to find the antidote, he is running out of time but it is bright sunshine when he injects her. Although it is very possible the sun would still be shining at 7 P.M., and particularly during summer time, the shadows cast during the fight with Ambrose show the sun to be close to high noon.