Continuity mistake: The tyres on the crotch rocket motorcycles they were riding kept changing from knobbly tyres to road slicks, back and forth depending on what terrain they were on. Easiest to see when Ethan skids on the road to avoid the white van - clear shot of slick tyres - then about 30 seconds later they're on the dirt, he skids into the old car and you can easily see that he's got off-road tyres front and back.
Factual error: In the scene at the race track where they show the virus infecting and destroying cells in the blood stream, they clearly show that it is red blood cells being infected. Viruses, in order to replicate, require the cell's DNA replication machinery. However, mature red blood cells in the circulation no longer possess this machinery since they no longer have a nucleus or DNA. It would therefore be impossible for this virus to replicate.
Continuity mistake: In the car chase scene with Nyah after they split and hit again and are spinning look at Ethan's car. The driver's side in the close ups was on the American side, then in the spin it is reversed to an English side. (It is a negative image - the license plate is reversed). The next image is back to normal.
Factual error: The action takes place in Seville, and the burning of wooden figures is shown as a traditional feast. The feast involving the burning of wooden figures takes place in Alicante and Valencia, 350 miles way from Seville.
Continuity mistake: The registration plate on Ethan Hunt's bike changes between 'NI 89' and 'ND 69' on occasion. Clearest moments are NI 89 just as he goes into the flames on the burning bridge, and ND 69 when he's through them. (01:38:35)
Continuity mistake: In the scene where Hunt is chasing Nyah in the car, there is a part where he almost hits a gray car. When the camera shot comes from behind, we see a gravel road on the side with pine trees, but when it cuts immediately to an air shot, we see a concrete bridge-like road with no gravel for several feet ahead or behind. It does this throughout the scene.
Visible crew/equipment: As Tom Cruise is listening to his mission via the sunglasses at the beginning of the film, the camera and several crew members are reflected in the right lens as the shot pans around him.
Visible crew/equipment: Near the end of the movie, when the point of the knife is close to Tom Cruise's eye, you can see the cameraman and the reflector on the reflection of the eye.
Continuity mistake: Tom Cruise is chasing Thandie Newton in his car in an early scene. He tries to fasten his seatbelt, and finally manages it. But later, sometimes he has his seatbelt on, and sometimes he doesn't.
Continuity mistake: During the fight between Ethan and Sean, Sean cuts Ethan's face with a knife and it's bleeding. A little bit later it is not bloody and it looks as if the wound is closed, then open and bloody again.
Visible crew/equipment: When the cars flip over as they blow up, you will see a circular object underneath the vehicles, about the size of a tyre. This is the device that "lifts" the vehicle for it to flip on one side, timed with the appropriate explosion.
Revealing mistake: During the scene on the beach just after the collision of the two bikes we see Scott and Cruise flying together in a big hug, but if you see the short shot when the black bike starts to explode frame by frame you will actually see a lonely man with his arms wide open.
Factual error: In the scene where Ethan is in the helicopter about to rappel into the BioCyte building, you see his hair blowing upward. In reality, the prop wash from the helicopter would make his hair blow into his face.
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: Why did Hunt's team decide to use an outback location as their Sydney base? It looks like it's in the middle of the Nullabor, which ain't exactly a helicopter ride from Sydney. Come to think of it, there isn't much terrain like that anywhere within a several hundred kilometres of Sydney.
Continuity mistake: When Nyah and Ethan are in bed in Spain, the lights reflected off Ethan's face and of the bed covers change between shots.
Plot hole: In the first night that Nyah is in Ambrose's house she meets with Ethan outside the house and they talk for about 1 1/2 min. Then we find out "Ethan" was really Ambrose with one of those "high-tech" masks. My question...After being in bed with both, how come Nyah didn't recognise Ambrose is about 5 inches taller than Ethan?
Revealing mistake: When Ethan's pal is in the helicopter and Ethan is escaping on the motorbike he fires a grenade launcher at the car - he misses the first time, gets the car the second time, but you can clearly see the bridge is made of wood - where the car gets blown up there's a big concrete/steel plate to support the bridge. (01:38:30)
Plot hole: The virus ravaged Nyah is making her way to a cliff to kill herself when Ethan sends his buddies to save her. There is no way that the flight to her location would have taken that long unless John Polson decided to take Ving Rhames for a guided tour of the Sydney skyline first just in case he missed any of it. It's just a couple of minutes flight time for a helicopter at full throttle.
Visible crew/equipment: In the scene where Nyah and Ethan have a race with a Porsche and an Audi-TT, at the end after the camera shows Nyah's feet you see both cars from front. Now on the right side of the screen you see the shadow of the filming helicopter.
Answer: Ethan did not want her to kill herself. Giving her a gun would allow her to do so.