When speaking about the warhead, the movie refers to it as being composed of "14.5 kilograms of uranium with a plutonium trigger". Some nuclear weapons can be loosely described in this manner, especially triple-staged thermonuclear weapons, but the terminology is very unconventional and the description is incomplete.
When Albert Gibson is in the Jetstar, the pilot says they are "on final approach" then tells Gibson they will be on the ground in twelve minutes, an extraordinary length of time for a jet to be on final approach. The pilot may have meant they would be at the gate in twelve minutes which would be reasonable.
When Helen drops the machine gun down the stairs and it shoots all the bad guys, in one scene it shows the gun falling off the last step and landing on the ground. In the very next scene, it shows the gun land ON the last step and come to a rest.
Although Helen was wearing the same outfit since being kidnapped from her striptease for Harry in the hotel, she is wearing less revealing underwear when she is in the back of the limo as the bridge is being demolished.
When Harry notes the missing page in the printout he stops his car on a sidewalk and the car's front wheels are straight. After speaking with Albert, Harry returns to the car and it's clearly seen that wheels are turned to the left.
During the bathroom fight scene when Harry pushes the 2nd terrorist's head into the urinal, the front of it is shown to be cracked and actually flexes like it's a separate piece. In the next shot when he handcuffs him, the crack is gone.
When Helen rebuffs Simon's advances in the trailer, one of the empty wine glasses on the coffee table falls over. When Harry's team enters the trailer moments later, the wine glasses are not only upright, but refilled.
At the beginning, when underwater, Harry is using an underwater welder to cut the gates, he is wearing gloves of a different style than when he emerges from the ice. When breaking through the ice, his gloves are more insulated.
When Aziz was kicking open the stall doors in the bathroom scene and Harry knocks down the stall door to escape, the angle shows Aziz standing far away from where Harry knocks down the door. The next scene (continuing this sequence) shows Aziz much closer and at a different angle when he starts firing his weapon at Harry.
During the scenes where Juno takes Helen and Harry to Samir to interrogate Harry, it is shown in several shots (but only briefly) when Helen is sitting on the stool that something is between Helen's legs/thighs. Upon closer inspection, it appears to be a hand grenade.
After Harry heads into the mall followed by the two terrorists, Gib tells Harry the third guy is still in the car. When Gib calls Helen, you can see the terrorists' car in the background. Before the bus pulls in to obstruct Gib's view of their car, you can clearly see the car is empty. Where did the third guy go if Gib was keeping an eye on him?
When Helen is about to leave the hotel room, just before the terrorists break in, the back of her dress is unzipped. Moments later when she is grabbed by a terrorist, the back of dress can (briefly) be seen zipped.
Just before her striptease assignment, Helen modifies her dress. At one point, she holds fabric she ripped from her sleeves as she tries to rip away the collar. Then, in a closer shot, the sleeve fabric is nowhere in sight.
In the limo fight scene, Juno's pistol is unloaded, hence the slide being pulled back, when Helen starts hitting her hand on the sun roof. When Juno lets the pistol go on top of the car, it is loaded again.
After Harry shoots the first terrorist in the bathroom, the other grabs Harry's gun-hand and Harry's sunglasses are still on. In the next shot where the terrorist is banging Harry's hand on the stall the glasses are no longer on his head.
Harry falls from his horse when it refuses to jump to the next rooftop, and is left hanging from the reins, which had been about four feet long, but now lengthen to almost twenty feet (to make a better shot of Harry dangling over the edge of the building.)
In the opening scenes, Harry's footprints go across a snow covered dock to an ice free lake. A cut has us underwater with Harry in his drysuit and there is the ice of a frozen lake above him. Harry exits the lake through ice.
During the chase in the hotel, when Harry first chases Aziz into the lobby, we see an older woman wearing a black fur with her husband almost get run over. After the two go through the hotel's various areas, ending up on the other side in the elevators, the woman and man in the elevator with Harry and the horse are the same couple they almost knocked over in the lobby. There is no way that same couple could have ended up there with Harry in such a short amount of time.
The Harriers fire 4 Maverick missiles at the bridge, meaning they would have each had to had 2 AGM-65 Maverick missile launchers suspended from the BRU-36 bomb racks in the wing pylons. The planes land on the highway afterwards with rocket pods and not Maverick missile launchers, which would be impossible.
When Helen drops her Uzi in the warehouse, it bounces down the stairs and kills nine of the terrorists before coming to rest on one of the steps. But in the last shot before that (as the bald attacker falls) it can be seen falling off the steps and coming to rest on the ground.
The height of buildings in Washington, DC is limited by the Height of Buildings Act to approximately 150 feet/15 floors. The Marriot in the motorcycle/horse chase scene is presumably in Washington, DC, but is much too tall for the city's skyline.
For the truck chase scenes along the Seven-Mile bridges, the terrorists are attempting to deliver the nuclear warheads from the Keys to Miami. They are driving on the older bridge with the newer bridge to the left, which means that the trucks are heading South towards Key West. If they were heading North towards Miami (as the scene would imply), then the newer bridge would be to the right side, not on the left.
While test driving the Corvette with Simon, the original dealer lot is on the west bound side of New York Ave. During the test drive the streets change dramatically from different directions of New York Ave and Rhode Island Ave all within the same context of conversation between the two.
When Simon is driving across the Francis Scott Key Bridge southbound, a shot of the Capitol building can be seen in the background. In reality, the Key Bridge goes from Georgetown to Arlington which is on the west side of the city while the Capitol building is on the east side of the city. The Capitol building is not visible from any point of the Key Bridge.
The Harrier cannot fire the gun while under 200 knots of airspeed - while hovering - because the smoke from the gun would be ingested into the engine causing a loss of thrust and an inability to hover.
Bullets fired from an AK-47 would not shatter the canopy on a Harrier jet. This was known by the filmmakers, but the shattered canopy was included to avoid having to worry about reflections on the canopy glass.
When Harry is talking on the radio in the minutes leading up to the nuclear explosion, he states that it is a "Bright Boy" alert. This alert does not exist in United States military nuclear incident terminology. This type of incident would be classed as a "Broken Arrow" (Unexplained or unauthorized detonation with no risk of full nuclear war).
When Aziz fires his AK47 at the stalls in the bathroom, it produces a "spread" that would be impossible to produce with an AK47 at that close of a range. Additionally, the bullets from an AK47 would have very easily penetrated the stall walls even back to where Harry was hiding.
The AGM-65 (Maverick) missiles fired by the Harriers were the AGM-65F, a massive air-to-ground missile that weighs over 650 pounds and is loaded with 300 lbs. of penetrating blast fragmentation high-explosive, only one of which would have completely obliterated the section of the bridge on which the vans were trying to escape. Experienced pilots, although authorized to fire, would never have spent four of these missiles on such a small target, and furthermore, the pilots would have fired from much farther away, given that the AGM-65F has an operational range in excess of twelve miles.
The drysuit that Harry is wearing at the start of the film has the zip across the back (this can be seen as he is pulling the suit off over his head). This type of drysuit is impossible to take off without help from another person ("self-donning" suits have a zip across the front of the body).
In real life the SS-22 designation was given to two missiles: a conventional anti-ship cruise missile and a theater ranged single warhead nuclear missile, neither of which is an intercontinental ballistic missile with multiple warheads as stated by Harry. Also no MIRV-carrying missile, which are strategic weapons, ever had a yield as low as 30 kilotons on the warheads since that is considered a low yield tactical weapon.
While Harry is escaping from the mansion, Gib is driving the van down a very icy road and the tires squeal with every swerve. Also, when Harry gets in the van and Gib takes off, the tires squeal again, all implying that the van was taking off on dry pavement rather than ice.
The Harriers used in the movie are AV-8B models. During the closing credits where credit is given to the Harrier model that was made for filming, the Harrier is said to be an AV-8A model. This is clearly wrong as the B model has a completely different frontal look to it then the A model.
When Harry is attempting to take off with the Harrier, you can hear the sound of the engine changing, sounding as if the RPM's were going up and down multiple times. The aircraft would be literally bouncing if that were to happen. When the nozzles are pointing down in the vertical takeoff position, those extreme types of changes in power is not done nor necessary.
When Helen drops the machine pistol, it continues to fire even though this would be impossible due the mechanism that prevents a firearm from firing if the trigger isn't pulled back. Also, despite only having a twenty round clip, the pistol fires at least fifty rounds before coming to a rest.
The when the lead terrorist, Aziz was videotaping his threat to United States, he described the island where he was, as "uninhabited". Of course with a bridge costing millions of dollars leading to that island, it was inhabited with people, but he's not going to tell the truth to the world when making a threat on videotape.
How did Aziz know Harry was in the bathroom? When Harry goes into the bathroom, one of the two terrorists follows him in before the other, so it's possible the second one, before entering moments later, quickly contacted Aziz and told him they had followed Harry to the bathroom.
When in the Helicopter, Albert says there are two Harriers that can be there in eleven minutes yet they show up just seconds later. However, it appears that each shot in the helicopter is jumping a few minutes. It is therefore possible that the Harriers did take the time indicated.
When Harry is outside the office building in the Harrier jet, you see a shot of a group of terrorists inside the building on one of the floors. They look out at the jet and Harry smiles back. The inside shots show the glass of the windows to have no tint. Yet on the other floors of the building you can see tinted windows on interior shots. Also the shots of the plane outside the building reveal that the glass has a mirror tint on it, and Harry could not have seen clearly into the building.
Harry doesn't need to see into the building as he has already been briefed by Gib that they are held up on the 20th floor. He's given this information just before taking the Harrier and is given the address of the building in route. Him smiling back at the terrorist could be attributed to him reaching the correct floor and/or coincidence.
In the scene where Harry punches Simon in the car, we cut to a shot of Simon with a bloodied mouth and nose. In the next shot, he has no sign of injury. This, in fact, is a brief fantasy sequence, showing us what Tasker would like to do to Simon rather than an actual event, hence the lack of injury not only in the next shot, but the rest of the scene.
The glass elevator into which Harry rides his horse looks to have a maximum capacity of about 10 people, so around 600kg. The horse he's riding would weigh well over that, so the elevator would not function. However, all commercial elevators support far more than their stated weight limits - they are usually suspended by either 6 or 8 cables, each of which can support the elevator plus 25% more weight by itself.
The terrorists are shown encasing the nuke that was detonated in several cubic yards of liquid concrete, the volume of which would have taken several weeks or months to harden given the thickness of it, thus rendering the process of submerging the bomb completely pointless.
Aziz is very upset when Harry attempts to conceal the fact that he knows what the warhead is, apparently because Aziz needs Harry's videotaped confirmation before the world will believe that he can detonate the nukes. But Aziz is well into preparations to detonate one anyway, long before the tape could have been delivered or broadcast. So the world will know when it goes off. There was therefore no need to threaten Helen or ever bring Harry to the island.
During the bathroom scene, when Aziz is kicking in the stall doors after shooting them, right before he kicks in the last door, there is a shot from inside the stall, facing the door. You can see the marks from the tape that was holding the squibs on.
In the scenes following the horse chase, during a briefing on who Harry was chasing, the video on the big screen is paused, yet the burned in time code for the video keeps rolling. If the timecode was indeed burnt in, it should have stopped, if it wasn't, there is no need for it.
When Aziz jumps his motorcycle off the roof, the trajectory is inconsistent with reality, as it shows him flying in a straight line into the swimming pool, when in fact he would have nosed dived to the street below.
When Harry is being chased from the mansion, he is attacked by two Dobermans. The Dobermans jump at him and get 'coconut crunched' together. The dogs used at that point were rubber. One of the rubber dogs' eyes pops out and can be seen flying off the right side of the screen when using frame-by-frame advance, as well when they fall to the ground they bend and crease like rubber (they also bounce).
When Harry chases Aziz through the hotel, Aziz blows by a bellhop who falls back into a chair, causing it to fall over. As is does, we see the spring-loaded device underneath the chair to assist it in pushing it and the bellhop back.
After the EZ Van has exploded on the highway on the bridge in the Florida Keys, shots from the helicopter's point of view show that what should be the burning wreckage of the van is in fact merely two flame throwers firing into the air.
When Harry and Gib are being followed by Aziz and two other guys in the station wagon, the view from inside the station wagon shows Gib pulling over and the station wagon pulling over. When it cuts to the view from inside Harry's car they are just pulling over and the station wagon is pulling over behind them.
On the island when Aziz fires the M-72 LAAW into the fuel truck, he extends the launcher but does not arm the weapon before firing the weapon. Just in front of the rear sight there is a trigger arming handle that needs to be pulled out to allow the trigger bar to depress and fire the rocket.
Early in the movie, when Harry is accessing the computer, which happens to be running a version of Microsoft Windows for what probably is Persian (Farsi). This language is written from right to left, just like Arabic and Hebrew. Harry types some sort of password into a pop-up window and the typical asterisks used to mask the password appear from left to right. They should have appeared from right to left.
When Harry is involved in the first chase with Aziz outside the Marriott, Aziz grabs a passing motorcyclist to take his motorcycle. The motorcyclist is moving past Aziz at a decent rate yet the bike drops right at his feet rather than skidding down the road.
When Harry places the cigarette pack with the hidden camera on the counter in the restroom, he turns his head left, toward the wall of urinals, to gauge the line of sight of the camera. However, he is wearing the glasses that transmit the image from the camera, so he would already be seeing the line of sight of the camera without turning his head.
When Harry is chasing Aziz through the hotel on horseback, Aziz rides his motorcycle through swinging doors into the kitchen area. When he slides the bike to make the corner, he leaves a black skid mark with the rear tire on the white tile floor. Seconds later, Harry bursts through the same swinging doors, but now there is a large piece of red carpeting covering the tile floor to prevent the horse from sliding as it runs into the kitchen.
The goof items below may give away important plot points.
The last part where Harry launches Aziz on a sidewinder missile that hits the helicopter: Sidewinder missiles cannot carry significant loads. The dry weight of that missile is about 140 pounds and adding an additional 190ish pounds would render it unable to fly properly.
Towards the end, right after the nuke goes off on the island,
in the next scene, the cloud is completely missing from the background. Clouds from a nuke explosion tend to linger on an on for hours at a stretch.
When the missile carrying Aziz blows up the helicopter, pieces of burning wreckage strike the glass of the building and bounce off, revealing that they are made of foam. Pieces of steel would almost certainly break the glass on the outside of a building.