Plot hole: The entire plot hinges on the villain's gang obtaining the tablet that allows admin access to the building's systems. However, it can only be unlocked via facial recognition and it is keyed only to Will Sawyer's face. In fact, when they finally do get it, Xia unlocks it by holding it up to Sawyer's face. So what was the point of trying to steal the backpack containing the tablet? Without Will to unlock it, the tablet is useless.
Continuity mistake: When they are first fighting, Will throws Ben onto the dishwasher. And as he rolls off it, there is a blue plate with a wooden spoon sitting on top of it. When Ben turns and grabs for a knife in the dishwasher, suddenly the blue plate is gone and replaced by various tupperware, and the wooden spoon is now standing up in a slot. (00:24:10)
Other mistake: A police helicopter nearly crashes and has to veer away because of the superheated air around the building when only a few floors are on fire, but Will Sawyer and everyone else can function normally when half the building is ablaze. In fact, everyone barely breaks a sweat despite being surrounded by flames.
Plot hole: Other than plot development, Why did Will Sawyer even need the tablet in first place? The tablet controls the building's "fire system" but he had already carried out of the building's analysis by then, and that also included the building's fire protection.
Continuity mistake: The small bandage on Will's left arm changes size through the film.
Factual error: It is absolutely impossible that the fire suppression system would still be operational at the end of the film. The fire would have destroyed all those systems ages ago, and even if the extinguishers / sprinklers themselves are resistant to fire, I doubt very much the cables that hook them up to the building's computer system survived intact.
Other mistake: Many of the scenes displayed on the monitors in the building and the local news footage of Will climbing the crane, swinging on the building ledge etc are depicted from a nice horizontal angle. There are no camera crews on the crane and there is no building nearby with such clear views. Nor is a news helicopter hovering filming the events yet hundreds of people gather to watch a huge screen as events unfold.
Revealing mistake: As Will and Ben are wrestling for the gun, it goes off, shooting Ben in the chest. When you hear the shot you can see the gun is lying on Ben's chest with him holding it, and it's pointed pretty much at an exact 90° to his side. It would have barely grazed him at best and would have left a long scratch/cut at that angle. Yet as they get up the shot is perfectly centered on his chest and round as if it was a direct shot. (00:24:55)
Continuity mistake: Ben tries to stab Will with a kitchen knife and he catches it in the stove bars. Will spins it around on Ben and is pinning him down, and the knife is pointed with the sharp edge up. But in the next shot, suddenly the knife is turned so the sharp edge is down. (00:24:30)
Other mistake: In the final fight scene, Will tells Bathos he is right behind him. Really? How? Bathos was facing a rather large hole in the floor he'd threatened to throw Will's daughter into just moments before.
Continuity mistake: When Zhao is realizing he's been locked out of his own system, he places his hand on the monitor perplexed. His hand is right under the word Authentication. In the next shot, his hand is suddenly to the left of the word Security. (00:34:30)
Continuity mistake: As Ben and Will are first going up the elevator in the tower, Ben mentions they needed someone like Will to check the math on their systems. One shot shows Will standing still looking at him in a close up, but in a wide angle it shows Will shift and turn a bit towards Ben. Then in the next close up shot of Will he's suddenly back to where he was. (00:10:50)
