(at around 2 mins) When Alexa is climbing the Lho La ice fall in Nepal, you can see a overview of the edge where is climbing to. There is nowhere a helicopter too be seen, yet after 30 seconds (duration of the phone call) the helicopter manages to land, turn off the engine (spinning down rotors takes much more than 30 seconds), and let Maxwell Stafford out of the helicopter and walk towards the edge to meet Alexa, all without her hearing or noticing a thing.
As the Predator ship passes by the Moon on its way to Earth, we can see the far side of the moon lit up, so from Earth it should be a new moon or at least a crescent. Yet, minutes later, it's a full moon.
Alexa's "warrior" marking on her left cheek disappears in overhead shots.
(at around 54 mins) The Predator cuts off the tip of the Alien's tail, spewing green acidic blood, and then tosses him through a column and into another room. As the Alien flies in slow motion, you can see that there is no blood on his stump, but immediately after, it's covered again.
Near the end. As the ship leaves Earth and the "person" behind, her shadow gets longer not shorter.
The film justifies the existence of a pyramid in Antarctica by saying that the continent once had a warmer climate with a lush ecosystem. This is true, but that was millions of years ago, not during human history.
(at around 9 mins) Icebreakers have round prows, not angled ones.
As in the Predator movies, there is an error with the Predator's infrared sight of humans attacking them: you always see the hot shells jumping away, but the path of the bullet is invisible. Because of hot gas and the heat of the bullet itself the path should be visible on IR.
Several characters, if not the majority of them, carry firearms. Under numerous international treaties, it is illegal to bring weapons to Antarctica. Most movies set on the continent tend to overlook this. In the novelization, Quinn does actually point this out to Sven, implying that the mercenaries are illegally armed, but the film does not address the issue at all.
The main character Alexa is ice climbing in Nepal. For a brief moment, it is possible to see her harness and she's carrying quickdraws, a type of gear that you only need when you're climbing with a rope (on ice or not). However, it possible to clearly see that she is free soloing, which means she's not climbing with a rope and therefore doesn't need quickdraws. A real climber that is free soloing would never carry quickdraws as they only contribute to additional weight.
(at around 29 mins) When the expedition first reaches the hidden pyramid, one of the characters examines the wall markings after rubbing away the cobwebs from the stone. Are there any spiders that thrive 2000 feet below sea level in Antarctica? Spiders and other arachnids have been known to survive in extremely hostile environments, including at high altitudes, in climates of intense cold and where food supply appears to be scarce. The climate inside the pyramid was warm enough that the humans' breath did not condense. Other survival factors may have been present. Also, the material may have not been spider webs, but strings of dust and particles accumulated over time.
The tunnel that the aliens "drilled" to the temple below the ice was said to have been done with highly advanced thermal equipment but yet the inside of the tunnel was ribbed not smooth. However, in nature such a process could indeed cause the ice to freeze over again in such a manner.
The legs of the practical and computer-generated Aliens don't correspond. The practical ones have human-like joints and feet, while the CG versions have an extra joint at the ankle and much longer toes.
Alexa is wearing only a thin sweater (and no hat) after the Alien burns her jacket, yet she doesn't even shiver while outdoors in Antarctica.
During the first battle, when the Alien falls to the ground after the Predator kicks it through a pillar, a wire can be seen holding its tail up.
Alexa is supposed to be climbing an ice-fall in Nepal, yet the helicopter waiting for her on top of the fall has a french registration (first letter is F). A Nepalese registration would start with 9N and an US registration, since the company is based there, would be N. Clearly the scene was filmed in the french Alps.
(at around 38 mins) Sebastian sets the clock on the sarcophagus to October 10, 2004 - 10/10/2004, because the Aztec calendar was supposedly based on 10's (the decimal system, erroneously called "metric" here). Yet, why would an Aztec civilization set a calendar to align with the Gregorian calendar, which is what our modern calendar is and wasn't developed until centuries later by the Romans? The Aztecs would not recognize what we call "October" as the 10th month.
In the movie the whaling station was abandoned in October 1904, when in fact it wasn't until the following month that the first whaling station, Grytviken (Cauldron Bay), was established in the Antarctic, and not at Bouvetøya, but in South Georgia. Modern whalers didn't reach Bouvet until the 1928-29 season, and these were operating with factory ships offshore. In 1928, the UK waived its claim on the island in favor of Norway, which had occupied the island the previous year. In 1971, Norway designated Bouvet Island and the adjacent territorial waters a nature reserve. Since 1977, it has run an automated meteorological station on the island.
(at around 20 mins) The penguin lurking in the abandoned Antarctic whaling station is a Humboldt penguin (Spheniscus humboldti), a species found in coastal Peru and Chile - not the Antarctic region.
The captions show the icebreaker approaching the island/pyramid from the Ross Ice Shelf. The island is in fact on the opposite side of the Antarctic continent.
In the unrated edition of the film, a satellite focuses in on Bouvet Island, but in that scene, the island is erroneously situated in the approximate location of Peter I Island, which is quite a distance from the actual location of Bouvet Island.
The island is referred to as "Bouvetoya Island" (the English name is Bouvet Island, "Bouvetøya" is Norwegian for Bouvet Island) but the real Bouvetøya is much further north and east than the satellite images suggested.
The satellite images show a large island west of the Antarctic Peninsula, no such island exists.
(at around 48 mins) It's claimed that the pyramid will move every ten minutes because the Aztec calendar is based on the "metric system". Time measurement has nothing to do with the meter. What he means is the decimal system. Modern measurement of time (24 hours in a day) is not decimal. Thus, each Aztec hour should be around 2.4 hours (1/10 of the day). As such, it would be more probable that the pyramid would move every 14.4 minutes.
The time-frame for the Alien life-cycle (from facehugger to chestburster to warrior) is made to seem like mere minutes in accordance with Sebastian's time-theory (10 minutes). In other Alien movies, the xenonomorph's life-cycle is established as taking hours or even days to complete.
Where did the dozens of aliens all come from? Considering that only 1 alien develops from 1 chest burster, that would make no more than 6 aliens total. (1 for each person that descended into the temple).
Considering the short amount of time spent in the temple, there was no way that the aliens could develop and mature in said time frame.
(at around 48 mins) Sebastian erroneously says that the Aztec calendar was metric (he means based on 10, which is not "metric", but "decimal"). In fact, the Aztecs had two calenders and neither was decimal. One was vigesimal (based on 20) with twenty days in 13 "months." The other was a 365-day year count.
(at around 37 mins) Sebastian refers to "the Long Count" while describing a calendar that he refers to as "Aztec". The Long Count was a feature of the Mayan calendar system; the Aztec calendar, although based on the Mayan, didn't use the Long Count.
(at around 11 mins) Graeme Miller's description of the aurorae as being caused by protons and electrons in the atmosphere is inaccurate. Aurorae are caused by the interaction of high energy particles (usually electrons) with neutral atoms (oxygen, nitrogen...) in Earth's upper atmosphere. However, as a chemical engineer, his knowledge of atmospheric photochemistry may be expected to be somewhat rusty.
Most of the weapons used by Weyland's team feature laser sights. Anyone with any kind of tactical sense or common sense would know that bumbling around with a bright green laser sight activated while being hunted by giant, stealthy monsters would be incredibly stupid. The laser beam leads right back to the shooter's precise location.
The date for the exploration is suppose to be Oct. 10, 2004, yet the camcorder used by one of the scientist shows the date as Oct. 8, 2004