In their first phone conversation, Gabriel tells McClane he knows him pretty well, as he's got all the info concerning him displayed, including all career records. Among the decorations received, we see he has been awarded a commendation in 1987 for the Nakatomi Tower incident in LA (referring to the events in "Die Hard"), and a citation for the swift resolution of the Chicago Airport Incident in 1990 (referring to those in "Die Hard 2"). This last record is wrong, as "Die Hard 2" was set in the Washington Dulles International Airport, and not in the Chicago Airport.
After the fight scene between John and Mai right before she kicks him out the window, her face is shown bruised with specs of blood on it and her hair was undone from the fight but after she kicks him through the glass, her face is shown again cleaned up without any specs of blood and her hair is neatly tied up in the back from when she originally fought him. As she approaches Matt, her face is back to being bruised with specs of blood on it and her hair is undone and out of the pin again.
When the bad guy ("Rand") jumps from the helicopter (as McClain crashes the police care into) his headphones fall off as he hits the ground. But when the scene jumps back to him getting up from lying on the ground, Rand's headphones are magically (and mistakenly) back on.
When McClane and Farrell are in the BMW the BMW Assist feature turns on. This function would be impossible since the service relies on a cellphone link and the cell systems were previously disabled by Gabriel.
Rand leaves Gabriel to go look for McClane and kill him. Later we see Rand finding McClane in the cooling room. But in between these two scenes we see Gabriel talking to McClane on the radio and slapping his daughter, and Rand is in the background, leaning against a wall. This editing mistake means Rand leaves to go look for McClane, comes back to Gabriel and waits, then goes to look for McClane again.
The CB radio frequency is 66.6 but CB radio is in the 27MHz frequency. 66.6 would be in the broadcast TV portion of the spectrum.
When stealing the BMW to go to West Virginia, Farrell sets off the airbag by swinging a trash can to set off the airbags. Cars need the key to be on and a stronger impact to set off the airbags.
When the pilot ejects from the F-35 jet, his parachute canopy takes several seconds to inflate and indeed, the chute is dramatically barely inflated just before the pilot hits the ground. Actually, the F-35 is equipped with the advanced Martin-Baker ejection seat which includes a parachute designed to fully inflate in one second or less, as pilots may need to eject from the aircraft at "zero altitude" (still on the ground) and still land safely.
Shooting a fire extinguisher will not cause it to explode like a bomb - at best, it will merely spew streams of its contents out thru any holes punctured in it.
While the bad guys may have been able to identify the IP address that someone was using, the name of the user does not come up. The best they could do is identify the ISP. Moreover, Warlock would be smart enough to have Internet access under a different name, at least his mother's.
All the way through the scene with the F-35 attacking the 18-wheeler, none of the other cars in shot are moving unless they are run into by the truck. However, the cars aren't moving because they have been abandoned.
After McClane busts the BMW's window to break in, he's seen driving moments later with a window up and whole again. However, it is the back window which is broken, not the front.
If there are three power substations for the West, Mid-West, and East, and you have to physically be there to shut them down, then there should be two more crews out there that McClane didn't stop. However, Gabriel's henchmen explicitly say that they shut down the West and Central grids, and they were waiting on Mai's, prompting Gabriel to radio Mai, leading to his exchange with McClane.
When Thomas Gabriel pulls up McClane's police record, the record displays McClane's social security number as only containing 8 digits. (This may have been done intentionally by the filmmakers to avoid the possibility of giving out someone's real Social Security Number.)
In the scene where the antagonists trace Lucy's cell phone to call her, the display depicts her SIM card number as "270A486FC78". In reality, none of the serial numbers used to uniquely identify a SIM card to a cell network are alphanumeric; they contain numerical digits only. This may have been done intentionally by the filmmakers to avoid inadvertently giving actual SIM card codes.
In the very first scene with Matthew, if you freeze frame the screen of his computer you can see the entire chat conversation he has with War10ck, which takes place about a minute later.
When Matthew is reading the name off of the registration card while talking to RoadAssist (0:59:27), the name Dvorak Tsajanski is handwritten, but the actual typed name on the card is David Seaver. However, assuming this person is an immigrant, "David Seaver" could simply be his Americanized name.
When all the street lights and turned green for the first time and John jumps on top of the vehicle to look at other intersections, you can clearly see farther away that traffic is moving fine and there are no accidents or traffic problems. Technically every intersection would be blocked and stopped and cars would not be moving freely.
After McClane shoots the driver of the truck, it sounds like the truck is shifting a gear up. Since the driver has been shot, there would be no one to shift gears. Furthermore, immediately after McClane gets in, it's shifting up again, although McClane is not yet driving the truck.
In a still-shot of McClane and Farrell driving along on the highway, it is evident that the shot was sped up to look as if they were going fast, and it is noticeable that their flashers were on as the car passes the camera (also note the long line of traffic behind the car).
Just after McLane turns up the radio playing the CCR song to wake up Farrell, the car is shown driving down the road with its 4-way flashers on.
At about 21 minutes in, as the helicopter is seen flying by, the sound is that of a 2-bladed main rotor helicopter like a Bell 206 JetRanger. But this helicopter is a Eurocopter AS350 Astar with a 3-bladed main rotor which makes a distinctively different sound.
Immediately after Trey arrives at the final location, Gabriel tells him to prepare the plane. A private jet large enough to transport at least twelve passengers is visible outside the building. The building is not located near an airport. It is surrounded by warehouses and other large buildings. There is not likely enough unobstructed space for such a plane to land or take off at the location. All of this begs the question, "Why not depart from an airport?"
After the West Virginia power station explodes and McClane and Farrell watch the electricity slowly shut down, there's a shot of an unspecified airport with the power going off. In that shot we see at least three Air Canada 747s taxiing or at their gates. Air Canada had already phased out and retired its entire 747 fleet at least two years prior to the year this movie was set (2007).
When McClane and Farrell are shown driving to West Virginia in the stolen BMW, the interior of the car is quiet, as if all the windows are rolled up, but the passenger rear window is clearly shown to have been smashed to gain entry (and smashing of the window was a plot point), meaning the wind noise from driving on a freeway would have been substantial and would have made conversation difficult.
When McClane is in the 18-wheeler, he looks out the passenger window at the fighter pilot and calls him a jackass, but you can clearly see he said jerk-off.
In the scene after the natural gas blows up the Middleton plant when Matt's giving up on 'winning,' his words don't match his mouth. Also, the same shot is used 3 times during his dialogue.
Right before McClane reaches the door of the 18-wheeler, the shadow of a camera can be seen on the side of the truck.
In the overhead shots of the police car McClane is driving during the chase scene with the helicopter, you can see the cameras stationed on top of the side view mirrors of the car.
There are no toll booths in Washington, D.C.
When McClane gets into the 18 wheeler after throwing the
driver out, a freeway sign can be seen out the front window marked 118 West. This freeway is in California, not Maryland.
At the beginning of the film, McClane's commander locates him at Rutgers University (in New Brunswick, NJ) using GPS installed in McClane's car. However, the map displayed on the computer on his desk shows a map of Philadelphia. (Trenton, NJ is shown in the upper right corner edge of the map). Rutgers is another 30 miles to the northeast - well off the map.
When McClane is driving the rig and being chased by the fighter jet, several shots of the Vincent Thomas Bridge are visible, which is in San Pedro, CA.
There is no Middleton, WV. Also, when Matt and McClane watch the power go out from the power station, the view that is shown is not a view of any city in West Virginia. No cities in the state are that big or that flat. (The "Welcome" sign, however, is completely accurate as of 2007.)
McLane and Farrel use RoadAssist (an OnStar type system) to start the car they steal remotely, but it has already been very well established that all forms of satellite peer to peer communication (including cell phones) are down at this point, so this would not work.
There is zero reason for the FBI to ask New York City to send an officer out of state to apprehend a suspect in Camden, New Jersey. New Jersey State Police or the Camden police would be asked apprehend the suspect. If the FBI wanted to do it themselves, they could send an agent from the Philadelphia field office as it is across the river from Camden.
Even if the terrorists had stolen a real government hazmat van (as opposed to simply painting a civilian van), it couldn't have been located since all the cell systems were down at that time.
While driving McClane and Farrell to the Federal building, the FBI agent calls DC Metro on the radio to have their officers clear a lane for them to DHS.
Despite Farrel and McClane not speaking at all at the time, somehow Gabriel's scanning equipment makes an exact voice match with Farrell and somehow they instantly know who McClane is, despite not having any connection to him prior to that.
There is absolutely no way they could have known who was in the car simply from the agent making a short radio transmission.
A big deal is made about the terrorists having to physically go to the power station to interrupt the grid. But even after losing security access to its computers, they are still able to blow up the facility remotely.
When Gabriel calls to the F-35 overhead, he identifies it as "AV Eighty-One". Real air traffic control or military command would have called it "Alpha Victor Eight One", using the proper phonetics for radio communication.
When Thomas Gabriel pulls up McClane's police record, it makes no mention of his time as an LA Cop (in 58 minutes pour vivre (1990) he explains he has switched to the LAPD to be with his wife).
Despite being incredibly hungry, apparently, Farrell ignores the Snickers bar in the glove box of the BMW they steal.
In the scene when Thomas Gabriel asks John McClane about his ex wife Holly and their divorce, the divorce certificate reads Holly's birth year as 1967 and John's 1955. The marriage year below reads 1979 in which is practically illegal since Holly would only have been 12 years old and not at the legal age of marriage even in 1979.
During his CB conversation with Agent Bowman while driving the 18-wheeler, McClane says, "If anything happens to me, send in the Calvary." Calvary is a name of a hill near Jerusalem used as a site of public crucifixion. What Bruce Willis obviously meant to say was "cavalry," which refers to a unit of mounted troops - formerly on horseback but more recently in helicopters and by other means. This error appears on the theatrical version, but not in the unrated version.