Continuity mistake: Near the end, after the huge gold heist, Simon Peter Gruber and his psychotic lover, Katya, engage in rough celebratory sex, ripping off each other's clothing, such that Katya's upper torso and black lace brassiere are fully exposed. A few minutes later, when John McClain interrupts their sex, Katya's shirt is fully closed.Charles Austin Miller
Visible crew/equipment: After the school evacuation scene starts the four kids trapped in the school look out the window to see what the commotion is. The next shot through the window grill shows a camera crew filming the evacuation from the street as they come up behind the cops on the upper right. Footage from the camera crew on the ground is proof of this. The footage is from the exact same time, about 30 seconds earlier in the movie. You see an African American boy and woman running off to the left of the screen through the police who are trying to guide everyone straight out from the stairs past the fence. The boy continues running but the woman is grabbed on her left arm by a cop who turns her back around to go through the fence. The boy is wearing a yellowish orange shirt and tan shorts and the woman in a brown outfit, a blouse with white buttons and pants. (01:40:10)DavidJ
Revealing mistake: When the bomb explodes at Bonwit Tellers at the start, we see a van fly into the air. You can see the devices that throw it upwards.