Character mistake: Just before the fire starts on the 81st floor, a man is shown telling an elderly couple that business offices only go as high as 80, and that 81-120 is exclusively residential. Not long after O'Hallorhan arrives, he asks Jernigan for a list of business tenants from 81-85, which Jernigan replies "most are yet to move in and those that have are not working at night". As said by the man earlier, these floors do not house business tenants, only residential. (00:12:05 - 00:43:45)
Suggested correction: Chief O'Halloran asked Doug for the floor plans from 81-85. He then asked Jernigan for a list of business tenants. Chief O'Halloran did not ask for businesses on any specific floor.
Character mistake: James Bond states that the man that fell in the liquid helium would raise the temperature. Since humans have a body temperature of only 98.6 degrees Fahrenheit, falling into a tank of liquid helium at -456 degrees would bring his body down to the same temperature as the surrounding helium in no more than five seconds. (01:49:20)
Suggested correction: The human body is mostly water which has a high specific heat capacity, much higher than liquid helium, so the amount of heat absorbed by the helium in order to cool the body to near absolute zero would easily raise its temperature well above absolute zero.
Character mistake: Juggernaut says to cut the blue wire to defuse the bomb. At the last moment, Fallon decides he's lying and so cuts the red wire and successfully defuses the bomb. But he failed to tell the other defusers this before he cut it! If he had guessed wrong and the bomb had exploded, the other defusers would have assumed he had cut the blue wire and so would also have cut the red wire and also exploded their bombs (or after the next bomb had gone off, they would have assumed the wire-color was random).
Character mistake: Near the beginning, Denise tells Stuart she has two small scenes in a movie, but then moments later tells him it is one whole scene.