Continuity mistake: The tyres on the crotch rocket motorcycles they were riding kept changing from knobbly tyres to road slicks, back and forth depending on what terrain they were on. Easiest to see when Ethan skids on the road to avoid the white van - clear shot of slick tyres - then about 30 seconds later they're on the dirt, he skids into the old car and you can easily see that he's got off-road tyres front and back.
Visible crew/equipment: When Dr. Okun is about to unlock "the vault", and says, "The freak show," a crewmember wearing a black and white striped shirt is hiding under the vault's floor, right behind Okun. (Only visible on fullscreen DVD.)
Plot hole: Why on earth would the military be interested in a soldier (sailor, aviator, whatever) who has to go into combat naked and unarmed, and who is detectable by an enemy equipped with a pair of cheap, mass-produced goggles? How would you treat them if they were injured? They would be utterly useless in any form of military operation, even espionage.
Factual error: During CONTROL's paintball training session, a barrel view of a bullet exiting the gun is shown as it travels to its target. However, the entire bullet is shown, casing and all, instead of just the bullet. (00:09:10)
Revealing mistake: When Dracula flies into the room to stop his brides from devouring Jonathan, the board carrying him is visible. (00:34:10)
Character mistake: The last time Doc tries the defibrillator on Norris, he uses it on the abdomen instead of on the chest. He also positions the pads incorrectly. They should be placed diagonal, with the heart in the middle, not horizontal.
Plot hole: Necros had absolutely no way of knowing that Bond and Saunders had arranged to meet at the café when they did and wouldn't have had anywhere near enough time to track them down and set up his elaborate booby trap. Saunders only suggested the meeting place and time a few hours earlier, and it was kept strictly between him and Bond. The scene in Tangier, where Whittaker tells Necros to kill another British agent, takes place on the same day Bond arrived in Vienna; meaning that Necros got from Tangier to Vienna (a 5-hour plus flight), tracked down Saunders, acquired the materials to booby trap the café doors (or had planned this ahead of time - unlikely), and set the trap up well in advance of him and Bond getting to the fairground. There was nowhere near enough time for all of that to happen without Necros having psychic knowledge of Saunders' movements.
Factual error: The movie is supposed to take place in and around New York City. However, during the car chase where Angelina and Brad are fighting off the three BMWs, a wide shot shows a street sign announcing Los Angeles.
Continuity mistake: In the British Museum, when Rick and Ardeth are saving Evie, Rick gives her a .45 pistol and they start to shoot the guards, her pistol fires once and the slide locks back meaning the pistol had no ammo, but she keeps firing as if the magazine was still full. (00:39:47)
Visible crew/equipment: At the end when Sidney's dad falls out of the closet, if you look closely you can see the hands of a crewmember who was in there too, pushing items out after him. (01:42:40)
Continuity mistake: During the infamous leg un-crossing scene when Sharon Stone is being interrogated, a cigarette in her hand disappears and then reappears.
Plot hole: This film is set in 2004. The thought that no search and rescue operations would be put in place after an aircraft disappeared from radar during a routine flight is absurd. The Chinese are paranoid about intrusion on their territory and the downed aircraft would have been located by a simple satellite search within hours of it crashing. Chinese military satellites crisscross the Gobi and they are equipped with optical cameras, microwave and infrared detectors and radar, so spotting a metal aircraft on the ground would be simple even if it was hundreds of kilometres off course. The crew would have been visited by Chinese military helicopters (and probably arrested!) as soon as the storm had died down.
Suggested correction: The Chinese government, for whatever reason, may have denied there was any crash at all if it suited their purposes, and the oil company that owned the plane would have little recourse. The Chinese have done this before. For the purpose of the plot, the survivors decided that they had to save themselves rather than wait for rescue and that was completely plausible.
Suggested correction: It's now 2021, and we still can't find Malaysian Airlines MH370. So this suggestion of planes always being found is laughable.
MH370 crashed into the ocean, and in fact some wreckage has been found. The Chinese military does not have the south Indian Ocean under satellite surveillance 24 hours a day, 365 days a year, unlike the Gobi desert where a crashed plane would be spotted within hours of it going missing.
Factual error: Based on the films being shown at the theater, the movie appears to be set in 1981. One of the TV commercials shows the Energizer Bunny, which didn't make its first appearance until 1988.
Factual error: The hat that Brad Pitt wears in the 1985 scenes is a Padres hat with navy, orange and white as the colours. In 1985, the Padres' colors were brown and yellow. The color change didn't come until late 80's or early 90's.
Revealing mistake: There are supposed to be two dead young Asian males sitting in the back of the car, but in this shot, it is so obvious that there are two dead 'dummies' riding in the back. Also, in the crash, a few seconds later, very blatant dummy heads are flying everywhere. (00:40:40)
Factual error: Towards the end of the film, Solomon is trapped in a small Plexiglas box and fires his gun into the bulletproof sides numerous times, but the bullets don't ricochet or get embedded in the glass.
Other mistake: In the slaughterhouse scene, after Harrigan has injured the Predator with his shotgun and Keyes reappears, the Predator throws its disc, and severs Keyes in half at the waist. We see his legs flop to the ground, and blood pour from above, but his upper half (torso, backpack and weaponry) mysteriously remain hovering out of sight. (According to the director, the MPAA made him cut the footage of the top half of his body hitting the ground because it was too gory, creating this odd error). (01:21:50)
Suggested correction: We don't actually know if the disc completely cuts Keyes in half (or just passes through him and leaves a gaping hole). You see the blood, but the movie is edited so that it cuts back to Harrigan looking on in horror for a split-second, then back to Keyes' body on the floor (mostly obscured by a cement pillar).
They blatantly show his legs hitting the ground without the top half! I can only assume you watched an edited-for-TV version or something. It's VERY clear in the movie that he was cut in half. (In actuality, the scene was the victim of the MPAA according to the director... they had to cut the bit where the top half of his body hit the ground because it was too gory... creating this odd movie mistake).
Visible crew/equipment: When Mrs. Peacock turns on the cellar lights, a piece of lighting equipment is visible to the left of the screen. (00:47:45)
Plot hole: In the end, all they have to do is ask the President, when he's conscious (Liev didn't kill him; he just knocked him unconscious), who killed everyone in the control room and nearly killed him. He would know who the traitor is and it's not Salt - when they look back at the facts, they'll see how Salt only killed when she absolutely had to, and how she saved lives and stopped a 3rd world war.
Visible crew/equipment: When Henry helps pull Mark onto the treehouse at the beginning of the film, if you look very closely to the left you can just make out a crew member dressed in black helping him on to the platform. The crew member then ducks back under the platform.
Suggested correction: Presumably the military are interested because Sebastian's research could lead to advanced forms of invisibility technology, such as the ability to turn materials and weapons invisible for use in combat.
You cannot second guess the film like that. Sebastian is making no effort to make non-living items invisible and throughout the film we see that is not possible (why else would Sebastian have to walk about naked?). His research is on animals (and later humans) not "materials and weapons" and is based on their physiology, anatomy and metabolism. How would you inject a rifle or a tank with a serum? They don't have a bloodstream. The military wouldn't see any value at all in this research - maybe they would be interested in invisibility, but not if it was restricted to living creatures as we see here.
You know how easy it would be for an invisible person to infiltrate an enemy's compound undetected and take out powerful leaders or dictators? Especially if no-one knew the technology existed.
Easy? Impossible. First, they would be naked and unarmed. Too bad if you are trying to knock off Vladimir Putin - a taekwondo black belt - with your bare hands during a Moscow winter! Being invisible doesn't mean you can avoid making a sound or triggering a pressure plate or an infrared detector and so on and so on. Final answer - a naked, unarmed combatant would be about as useful as a chocolate teapot in any form of operation, covert or otherwise.