Corrected entry: The S.H.I.E.L.D. helicarrier has the number 64 painted on it in several places. 1964 is the year the first Avengers comic was released.
Corrected entry: In Iron Man 2, Stark makes the new triangle thing that's saving his life and he has it throughout the Avengers, suit on or off. But in the last battle up from when he jumps out the window after his little chat with Loki to the end, he has the other one, the circle one that was slowly killing him.
Corrected entry: In the scene where Thor is dropped from the cell chamber, the ship is supposed to be in free-fall, having lost 2 engines. I've seen this a few times now, and I'm pretty sure the one Iron Man is restarting isn't back on, and the second one has been disabled. If this is the case, Thor should not fall. Neither should the characters running about the ship be experiencing gravity.
Corrected entry: Helicopters work by creating a low pressure zone above the rotors, by forcing the air down. In other words, sucking air away from the top side. Since the helicarrier is basically a giant helicopter, it's lifted by rotors, it should be sucking air in from the top. But judging by the way Banner's jacket blows, it's blowing air out.
Corrected entry: Thor's hammer has a slightly altered appearance in this film from how it was seen in Thor. Where before it had a mostly brown handle with a brown strap at the end, now the end of the shaft has a silver cap, with the brown strap connected to each side, and the handle is more prominently ringed by silver. While some may rationalize this by suggesting maybe Asgard redesigned it between movies, remember that this is an ancient weapon and the Asgard do not seem like the type of people who would alter their holy artifacts with superficial changes.
Corrected entry: When Iron Man tells the others what he intends to do with the missile, Captain America says that it's a "one-way trip." But, once he aims the missile at the Chitauri ship, Iron Man could have let go and returned through the portal. The missile would have kept a straight course at the ship; he wouldn't have had to keep flying with it.
Corrected entry: During the scene where Tony is "threatening" Loki in Stark Towers, he gets a glass of alcohol and drinks it as he is talking to Loki. He is then picked up by the neck by Loki and is thrown to the ground, and his glass is nowhere to be seen. It is not seen dropped or shattered, and it is clear he did not have time to back up and put it down. (01:37:00)
Corrected entry: The nuclear missile that is fired at Manhattan, the Air to Ground (AGM)-154 Joint Standoff Weapon (JSOW) does not actually have nuclear capability. The F-35 Lightning II, which fired the missile, however, can actually carry the JSOW and will eventually be able to carry the B61 nuclear bomb.
Corrected entry: When the arrow explodes aboard the ship Captain America [already in his outfit with long sleeves and has auburn hair] tells Tony Stark [wearing a long sleeved shirt, black hair] to suit up. They both leave but one of them can be seen running seconds later with auburn hair and a short sleeved t-shirt. (01:12:35)