Factual error: When they're first entering the whaling camp, a penguin startles Miller. That penguin was a black-footed penguin, which is a bird native to much warmer climates. If that little guy had actually been in Antarctica, he would have died within minutes.
Continuity mistake: In the scene where Lex is running in the abandoned whaler camp, the "shield" she is holding keeps changing hand between shots.
Continuity mistake: Early in the movie the female protagonist "Lex" Woods is climbing an ice waterfall. The scene shown from a distance reveals a steep ascent above the ice, but in the next scene, she reaches a large area flat enough for a helicopter to land upon.
Visible crew/equipment: During the briefing Weyland says "But it's not on the ice, it's two thousand feet below it" it cuts to a shot behind Maxwell with an overview shot of the crew. If you look behind Maxwell you can see the tip of a head moving into picture. In the previous shot we could see no one was standing behind Maxwell, and it couldn't be Sebastian cause he went back to his seat.
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.
Factual error: The expedition leader claims that Bouvet Island is not under any national control, because of the Antarctic Treaty. However, because of its remoteness from the continent of Antarctica, Bouvet Island is actually not included in this treaty and Norway has full ownership of this island.
Factual error: When arriving in Antarctica, there is dialogue about the full moon (la luna di cacciatore, etc...) There is no full moon on 10/10/2004 in Antarctica. But it does look nice in the movie...
Continuity mistake: When Lex Miller and Sebastian are talking at the side of the ship at the beginning, Miller says "Ii wish you'd consider coming with us ", it cuts to a shot from the side/back, she is looking either in Sebastian's direction or out to sea, yet in the following shot she is looking at Miller's face.
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.
Continuity mistake: Close to the beginning, when the group is inside the pyramid below the sacrificial chamber, when the shot is from behind Lex and the others, note where the green light is, directly in the middle of the stairs. When it cuts to an overhead view, it's more to the left than the right.
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.
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.
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.
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.