Other mistake: When the security system is armed, you can see the barricades are smooth steel panels running inside the outer walls, obviously on runners. Now, how do you attach a chain to a smooth steel panel and how do you rip it out without bringing the whole wall down? When Charlie lets the fugitive in, the panel is at least 1in thick. There is absolutely no way anyone is getting through that without specialised tools or heavy machinery.
Other mistake: During the climactic gunfight Jay Swan retreats to his car. Using his binoculars Swan looks to the left and slightly rear of his car to see Pete Bailey (who is shooting at him with a high-power rifle). Bailey fires a shot at the car and the bullet strikes the front windshield (an impossibility from that angle). (01:48:00)
Other mistake: When Stig shoots the helo and kills the co-pilot it still crashes. He killed the co-pilot, the pilot sits on the right side. (01:36:30)
Other mistake: When Estefania and Amadeu first meet, she attempts to light a cigarette while talking, which is impossible - you have to have both lips together to hold the cigarette still for the match to light it successfully.
Other mistake: Ten minutes into the movie, during the credits one character is presented as "Cheno", but in the end credits he's "Chino". (00:10:35)
Other mistake: In final 14 minutes, the greys are attacking the house. Several screws are "unscrewed" from the plywood. The first two are turned the wrong way, and the sound effect is of tightening. (01:23:54)
Other mistake: When the title card "FLYING MONKEYS" appears on screen, during the opening fly-over shot, if you look near the bottom right of the screen you can see something briefly move into, then out of, shot. (00:02:28)