Continuity mistake: When Hauser picks up the Admiral, after the Brain Bug attacks them, she has no yellow alien blood on her as she's being pulled up, but when the shot changes, as she's standing up, she now has blood on her face and uniform.
Factual error: The moon is full every night the highschoolers are at the lake house.
Continuity mistake: When Bella and Edward talk in the woods, Bella drops her backpack in front of a tree. In a subsequent shot, the backpack has disappeared. (00:49:55 - 00:50:55)
Continuity mistake: When Seth has been sliced by the blade, he spits blood that goes all over his face. It then cuts to Hoffman looking at him, then back to Seth, and now the blood on his face has gone. This happens three or four times. (00:05:10)
Factual error: The aircraft used to fly to Shangri-La is a Bristol Beaufighter, a single seat long range fighter bomber. It was not a transport aircraft and could not carry passengers. Some variants of the Beaufighter were two seaters but none at all could be used as small airliners as they do here. It is not possible to simply reconfigure the aircraft as shown here - the centre of gravity, balance and trim would all be thrown out. The resulting jury-built aircraft would be uncontrollable in flight.
Continuity mistake: James takes off his tie to cover the cut on Kristen's hand, but when they run outside to escape in the car James is wearing his tie again, then after the failed escape they run back inside the house and James tie is missing. In another scene Kristen goes into the woods to look for James and falls into a ditch, then as she climbs out the tie is missing from her hand, but the next scene it's back in place.
Audio problem: Right before the end credits, as Grave Robber says "But Genco may survive if it undergoes surgery", right as Grave Robber says the word "may", his lips briefly don't match what is being said. (Confirmed in DVD commentary.).
Other mistake: Even though the building is said to not have power and the guards have to use flashlights, the first time Keiffer goes in the basement he is able to flick the switch and turn on the lights.
Character mistake: Jeff mentions Mathias could have septicemia which he says is "a bacterial infection usually in the bone" However as a medical student he should know that septicemia means blood infection and has nothing to do with the bone.
Audio problem: During a scene where Donna is exiting her hotel room, she runs into Clair and both scream. However, Clair's scream cannot be heard, but an odd screeching sound is played in place of her scream, which continues even after her mouth has been closed.
Factual error: When you see the blind Syndey walk through her appartment she keeps touching the walls to feel where she is. A person who has been blind for over 20 years (as is mentioned in the film) knows the way around their own home. They know preciseley how many steps it is from room to room. They wouldn't keep touching the wall like this.
Continuity mistake: As Ben and Jane drive down the road, it is raining. After they hit the ghost, the scene fades to black. When the scene fades back in, it's heavily snowing, and a previously nonexistent thick sheet of snow is covering the ground. As they get out of the car, they start talking. During their conversation, there is a quick cut, and with this, it instantly stops snowing.
Continuity mistake: When Oskar shows his Rubik's Cube to Eli and explains how it works, one side is all white except one square, which differs from being red vs. blue between shots.
Plot hole: One of the flying dragons impacts the right outer engine of the B-29, and the fire spreads to the right inner engine. The crew lands the plane on the island, and the girls rebuild both engines, despite the fact there are no parts available on the island.
Factual error: All the soldiers that have rolled up sleeves have them rolled up Marine style (with the inside of the sleeve showing) despite being US Army.
Character mistake: On Taylor's phone it says she dies at 8:32PM, but Beth says 7:32PM, when reading the message. (00:27:05)
Revealing mistake: When Ami's chest is being drilled by the "drill-bra" at the end of the movie, you can see blood flowing from her chest, obviously because of the damage the drills are causing her. Yet, later, you can see absolutely no cuts or marks on her breasts or upper chest, where the drills were penetrating her skin. The skin is simply soaked with blood.
Continuity mistake: When Nick and Bobby are playing craps in Rusty Nail's barn, Nick rolls "chest," resulting in Rusty branding Bobby with his R key chain. Rusty puts the red hot key chain in Bobby's shirt pocket and holds it against his chest. When Rusty lets go, you can see a hole has been burned into Bobby's shirt. The very next shot, Bobby is rolling the dice and his shirt is intact. Later on at the very end of the film, Bobby's shirt has the hole in the pocket again. (01:13:50 - 01:15:00)
Continuity mistake: In the scene where Lloyd is briefing his team about the events of the next few hours, there is a shot in which he says the words 'weather systems' as someone walks across the screen from the right. Immediately the camera cuts to a close-in shot of Lloyd. But right at the end of the scene, the exact same shot is shown again, minus the sound of Lloyd saying 'weather systems'.
Other mistake: It is crucial to the story that Peter is terrified of moths - but when he is led through the woods at knife point by Tracey, a large moth flies around both their heads for several seconds (lured by lights of the film crew) and he ignores it, being as it's an unplanned visitor. (00:42:30)