Factual error: Throughout the entire movie, Arnold and Tom are always riding in the GM S-series SUV. The thing about these vehicles is that they came with different side view mirrors and if you look close enough during all the shots with the SUV, the side mirrors on the side change, from small ones to big square ones, showing that two different GM S-series SUVs were used throughout the movie.
Visible crew/equipment: During the Corvette scene when Arnold is driving, there is a shot looking at Bill Paxton talking and on his shoulder is the shadow of the boom mike. (00:55:10)
Revealing mistake: When all the terrorists are firing their guns at the sky near the end, one of the men is clearly pulling the trigger, and empty cartridge cases are coming out, but there is no muzzle flash like the other guns.
Factual error: The shots fired in the toilet are fired at a very narrow angle at the toilet doors. But when you see the holes up close they are perfectly round. They should be elongated. (00:32:40)
Continuity mistake: When Harry goes over the Marriott hotel roof, he switches from being over the "a" to being over the "r", depending on which camera angle it is.
Continuity mistake: Arnold discovers about his wife's lover. He crosses the street dazed and passes by a bus. When the angle changes he is several meters behind and starting to walk towards the bus again. (00:43:55)
Continuity mistake: During Harry's Tango with Juno, she bends backwards twice, the second one a couple is dancing right behind them. In the opposite angle it's a different couple and they're walking. (00:10:30)
Audio problem: In the scene where Dana's about to fall off the crane, you hear an audio of her screaming "Help me. Help me." But if you look at her face, she's not saying anything. (02:08:15)
Audio problem: When the motorbike drives through the Marriot - on carpet - its tires makes sounds as if on concrete. (00:35:50)
Factual error: When Harry's wife is meeting the used car salesman, he says to meet her under the Key Bridge on K street, that would be hard because the Key Bridge is actually over the Potomac river. If that scene was shot in DC it is on K street, under the Whitehyrst freeway. (00:57:30 - 00:58:50)
Revealing mistake: When Helen drops the machine gun down the stairs and it starts shooting, watch the railing with the broken splinters and you'll notice that we are always seeing the very same shot repeated over and over again.
Continuity mistake: When Harry and Gib are interrogating Harry's wife, she says a line "I don't give a s**t if you understand that or not," and the shot is a close up of her on the heat screen. Notice that her head is tilted down. However, when the shot cuts to the wider angle you can see the heat monitor and her head is instantly at a more upright angle without time for her to move. (01:10:10)
Continuity mistake: When the limo is on the bridge and it runs through a burning part, the pavement is filled with debris scattered all around. When Harry's chopper flies over the place, the pavement is clean.
Revealing mistake: In the restroom fight scene, the first villain shot by Arnold randomly shoots his gun as he is dying. Some of the stray bullets hit the urinals. As the camera angle changes to show the bullets hitting the urinal, large flames can be seen as the urinal explodes and falls to pieces. There must have been a small explosive used to make this happen, as the bullet impact wouldn't do this. (00:30:00)
Revealing mistake: Right after the horse motorcycle chase scene, at the next day's debrief, there is a piece of file footage showing the lead terrorist. As per normal practice, there are numbers running in the clip to show where they are in it, however, even when they pause, the numbers continue to run. Most visible when Trilby asks why he's called the 'sand spider'; they pause the tape and yet the play numbers continue to run. (00:41:55)
Continuity mistake: Before Salim Abu Aziz kicks the bathroom stall doors, we can see there are 6 stalls (and Harry is in the 6th one). Salim kicks the first door, but the close up shot shows it's at least the 2nd door since we can see a door to the left of the post with the lock on it. After that he kicks the 2nd and 3rd door. After he kicks the 4th door, Harry crashes out of his stall, but he's 3 stalls over instead of 2.
Continuity mistake: While being interrogated, Helen slams a chair against a glass. The damage done increases and decreases randomly all the time. (01:11:05)
Continuity mistake: At the hotel, when Helen is about to destroy her dress she places her gabardine on a bench, to the right of her bag. In the next 10 shots, the gabardine's position and the way it's folded keeps changing. (01:18:05)
Continuity mistake: During the bridge scene the limo driver is shot and blood splatters on the windshield. In the outside angle the blood is gone. (01:55:20)
Visible crew/equipment: In the scene where Bill Paxton and Arnold are riding in the Corvette, you can see a camera reflected in the windshield on several occasions; most notably just after Arnold takes the wheel. (00:55:15)
Chosen answer: He didn't really. Harry just knew he was heading up. He pressed the top floor to get the elevator moving and kept an eye on him on the way up. If the terrorist's elevator suddenly stops, Harry can press the button for that floor to stop his elevator.
XIII