Continuity mistake: When the loader is dragged into the airlock, the yellow caution light shatters. The light is fully intact in the next shot.
Factual error: The marines' rifles are supposed to fire "standard armor-piercing rounds", which should have done way more damage than producing a few sparks on the frail sheet metal table in the med bay when Hudson shot the face-hugger threatening Newt. "Standard AP rounds" would have pulverized the table and created a huge hole in the wall behind it.
Continuity mistake: When you see the attack aircraft flying towards the planet from the front you can see the pilot Ferro in her dark glasses sitting on the right side of the cockpit, but in all the other close up shots she sits on the left side with Spunkmeyer behind her on the right.
Continuity mistake: Hicks has a heart painted on his armor with a latch locked by a padlock. When Hicks and Ripley enter the elevator after losing Newt, the padlock is missing. After the Alien attack, the padlock reappears.
Continuity mistake: At the start of the film when you see Ripley in her stasis capsule the glass is clear, but when the salvage men enter the shuttle craft the glass on the capsule is covered in frost which one of the men has to wipe away in order to see her face.
Continuity mistake: From Director's Cut. The scene where Al is being quizzed about the ownership of the discovery of the object discovered by the "Mom and Pop" survey team tells us that a call has been put in by that team to the base. But then when they discover the ship, where is the call? They explicitly do not call it in. Now this is not just a general enquiry because they were sent out there two weeks ago to a specific grid reference. "He says he's onto something." (00:16:34 - 00:18:38)
Continuity mistake: When Ripley loads the magazine into the gun as she prepares to rescue Newt it says 95 rounds but when she is going down the elevator shaft it says 42 without her firing a shot.
Revealing mistake: When the swarm of aliens drops through the ceiling panels, you can tell that Ripley and the marines don't have magazines in their rifles. It's especially visible when Ripley looks up before Hicks raises the panel and sees the aliens.
Visible crew/equipment: When Ripley is first shown in the loader after asking Apone if she can help, after the loaders claws grab the crate and she swings the crate around and asks "where you want it?" you can see tubes trailing off to the left of the loader that don't connect to anything in frame. The tubes are on the right side of the frame just under the crate in the loader's arms.
Revealing mistake: The "mission time" clocks on the video screens are very inconsistent most of the time they're seen. At several points they jump back and forth from 00:01:31 to 00:01:32 then back again even though all of them are supposed to be synchronized.
Continuity mistake: When the team approaches the colony entrance to open the outer door, all the marines are inundated with pouring rain. Yet the moment they enter the compound and start searching, they are all dry.
Other mistake: The POV shot when the alien kills Burke is reused minutes later as the shot of the alien attacking Gorman and Vasquez as the grenade goes off.
Other mistake: When Hudson is looking for bios on the screen, it shows them on level 3. But when Frost falls down the hole after being hit with a flamethrower, he falls down a number of levels.
Other mistake: They should have had much more than only twenty-six minutes to save Newt. Bishop said that the reactor would blow in four hours after seeing the emergency venting. He said it would take forty minutes to crawl down that pipe, an hour to patch into and align the antenna, thirty minutes to prep the ship, and fifty minutes flight time. 40+60+30+50=180 minutes, gives them an hour spare.
Suggested correction: And how are you so sure everything went smoothly without problems? Any of those things could have taken longer, leaving only 26 minutes.
