Continuity mistake: In the scene when the Predator is impaled on the Alien's tail, there is Predator blood all over the Alien's tail. When the Alien flings the Predator's body away, the Predator blood on the Alien's tail disappears. (00:52:30)
Factual error: When the predator starts to kill Weyland, Weyland uses his oxygen tank as a makeshift flame thrower. Contrary to popular belief, oxygen does NOT burn. It only allows other things to burn. The three things needed for a fire are oxygen (which he had), fuel (which he did NOT have) and heat (from the flare he lit). (00:59:25)
Continuity mistake: When the main Predator kills his first alien, he concludes the 'rite of passage' by burning himself on the forehead with alien acid. This should have left a circular mark on his forehead, but when we see him at the end of the movie, he only has the 'tau' symbol. (01:00:35 - 01:20:40)
Factual error: The Desert Eagle that Miller & Lex use to shoot Aliens can hold a maximum of 9 rounds in .357 Magnum. Yet they fire quite a large number of shots from the same gun without reloading. High-capacity magazines are unavailable for the Desert Eagle as the magnum rounds are just too big. (01:02:45 - 01:14:00)
Continuity mistake: When Alexa and Sebastian are walking down a passageway in the pyramid, after everyone else has been killed, they begin to hear aliens all around them and look around. When Alexa shines her torch at an alien, she is on Sebastian's right side, but in the next shot she is on his left side, and her small torch vanishes from her right hand. (01:05:10)
Continuity mistake: When Lex and the predator are going up the tunnel at the near the end of the movie. Lex has the alien head shield on her left arm. But when they are speeding up the tunnel, the shield is not on either arm. If you pause it, you can see the shield missing. When they emerge out of the tunnel it is back on her arm. (01:17:05)
Suggested correction: The shield didn't vanish. Lex removed it so that she could hold the sled with both hands. The shield is right between Lex and the predator. (1:26:58) When they emerge out of the tunnel, the shield is on her right arm.
Continuity mistake: In the scene where Lex is running in the abandoned whaler camp, the "shield" she is holding keeps changing hand between shots. (01:18:05)
Continuity mistake: When Lex and the Predator are running through the tunnel and neither of them has the spear that the Predator built for her. Then later spear is back. Then after the sled crashes, its gone again. For the remainder of the sequence, the Predator has it. (01:19:15 - 01:20:40)
Continuity mistake: At the end compare the shots taken from the top when the predator is lying dead over the snow; right after he dies and when the other predators are going to pick him up. His left arm changes position and his "rasta locks" are spread in a different pattern. (01:23:40)
Continuity mistake: Lex's initiation mark disappears in overhead shots.
Revealing mistake: After the predator drops Weyland, as the predator turns, you can see the skin of the actors neck.
Factual error: The members of the expedition are wearing their Snow Goggles on their hats with the lenses to the front. However, anyone who has ever worked in a cold weather environment (especially the guide and her "7 seasons on the ice") would know that the goggles should be worn backwards if they're not over your eyes. This keeps them from getting moisture on them.
Factual error: The movie takes place in the first half of October which is the beginning of the "Antarctic summer" not that far away from the Antarctic circle. That means there should be a lot of sunlight and sun should only set for couple of hours. However all the exterior scenes in Antarctica are shot in darkness.
Continuity mistake: Towards the beginning, in the scene where they are first going down the tunnel, and the one guy slides out of control. When the woman uses her pick axe to stop him, she slams it into the tunnel before he passes, and his jacket catches on the ax. In the next shot, the axe has struck the jacket in the middle, the jacket is no longer "hooked" on the ax.
Continuity mistake: Lex gets the Predators glowing green blood splashed on her clothes when the alien kills it. Next shot her clothes are clean.
