Revealing mistake: When McClane goes into the icy room in the power station, look at the pipe to the side of the acrobat: it's in shot a few seconds and you can see that the writing on the pipe is reversed, revealing that in the editing room, the shot was flipped.
Revealing mistake: Airbags are made out of a super strong fabric material with heavy weaving. There's no way McClane would be able to tear it. You can see the texture difference between McClane's fake airbag and the real passenger side airbag.
Suggested correction: Incorrect, the driver's airbag is designed in such a way it can be ripped out. This is a safety feature to be used in a life or death situation if the car is still driveable. For instance, if someone rams you off the road and the airbag deploys, you can rip it off and continue driving to try and escape the assailant.
Revealing mistake: Just after the F-35 explodes there is a shot of the flames receding up the ramp McClane slid down. Also in this shot, Rubble goes uphill, showing the shot was reversed. (01:51:20)
Revealing mistake: In the tunnel, as John does the 180 handbrake turn, if you look on the floor you will see skid marks exactly where he performs the 180 turn. Clearly from previous takes. (00:40:00)
Revealing mistake: When the bomb explodes in Farrell's apartment, you can see the man in the room who gets blown against the wall is a dummy.
