Other mistake: Where does the fire in the gas pipes come from? Even though a lot of gas - and thereby pressure - is directed towards the power station, why do they blow up under ground far away from the power station?
Suggested correction: The pressure caused a pipe to crack or similar, and some gas leaked out to where it shouldn't be, and it got ignited. You couldn't count on that happening, though. The idea was probably to have the pipes/valves blow out at the power station and flood it with gas.
This isn't a strong correction, especially as it admits that it likely wouldn't have worked and uses a lot of conjecture.
Factual error: 0.7% of the electricity generated in West Virginia (as of 2011) is from natural gas. The plant in the movie would have been a peaking unit, only operated during the day. Shutting down a power plant that is not operating would not cause a black out. Further evidence that the unit is not operating is that only three security guards seem to be on the premises. You can not operate a power plant with three security guards.
Suggested correction: As I understood it, the original idea was to use the power plant's computer to shut down the power grid, not the plant itself. How the explosion then accomplished the same, I have no idea.
This correction does not actually address the mistake properly.
Continuity mistake: John M is driving to the Eastern electricity station and chatting. The view out of his window shows him driving past the same distant hill at least three times. Also the speed is faster out of the passenger's side than the driver's.
Corrected entry: McClane's daughter is caught in the lift of a high rise when the power turns off. When she is rescued she is - minutes later - at the main computer facility outside of Baltimore. How did she get there so fast? She lived in Jersey close to NYC.
Correction: The film doesn't at any point say that Lucy was in her home town, she could easily have happened to be near by, or near enough for her to be flown quickly by helicopter.
The goon who got her out of the elevator said he was with the FBI Jersey office.
Question: How did the emergency operator start the car when Matt tells them to start? And why did Matt do so when McClane was ready to start the car with just the wires?
Chosen answer: The on-board assistance system that Matt was using to contact the operator is specifically designed to allow for emergency usage in just such a way. They usually require a password to verify the user, which is exactly what Matt was trying to BS his way around. However, even though McClane is willing to hotwire the car, there are two problems with this. First, cars in recent years have become much harder to hotwire. Second, even if McClane was able to do it, the on-board assistance would have been triggered and it would assume (rightly so) that the car was being stolen and authorities would be alerted. With a likely GPS in the system, it'd be hard to get away from that one. By using and fooling the system, they now have the ability to get around unencumbered.
Also, the airbags wouldn't have deployed when he hit the bumper with a trash can. They're designed to go off only when the vehicle is in motion thanks to a vehicle speed sensor that arms the system over a certain speed to avoid costly repairs in the event you just bump something or vandals just wanna be vandals. I remember a funny commercial with an elderly woman using her purse to hit a car bumper when the driver honked at her as she slowly crossed the street. Hilarious, but not accurate.
Plot hole: Since they took down the telephone network, it would have been impossible for Justin Long to even be speaking to the emergency response woman for the car, much less send a signal to start the car up.
Suggested correction: Is it possible this is a satellite phone call akin to Onstar?
No, the BMW system requires a cell signal to work, which was taken down earlier in the movie.
Corrected entry: When McClane is driving the semi chasing the Haz-Mat van, he radios Warlock to patch him through to the FBI. After getting patched through he tells the FBI agent that he is chasing the van onto 695. 695 is the Baltimore beltway. There are noelevated highway sections over the Baltimore beltway the way the movie depicts.
Correction: These elevated over-passes were added to the sequence to set up the later chase scenes and for dramatic purposes. Therefore, no mistake here.
That's still a mistake since the overpasses don't actually exist. It's supposed to be 695 and looks absolutely nothing like it.
Corrected entry: As Gabriel is starting the download from Woodlan to the "portable" server set up by his men, the progress bar shows "0 of 500TB used". Even with today's harddrives, one would need to carry 250 to 500 harddrives to reach this capacity.
Correction: Gabriel didn't download the data to a portable server. His men went to Woodlawn to disable all the safety protocols (firewalls etc) and the download was completed via the normal Internet to a server farm elsewhere. This is why Gabriel turned off phone networks, satellites etc to make sure he had as much bandwidth available as possible for his download.
Corrected entry: In the scene where McClane is in the truck being chased by the jet plane, the truck is attacked by missiles. In a particular shot a missile blows up the road making the truck almost flip-over. The truck is in a hard LEFT-turn. McClane steers hard LEFT to prevent the truck from flipping over. But that would only make the truck flip harder. He should have steered hard RIGHT.
Correction: The trailer portion is trying to flip overto the right. He steers hard left to try to counterbalance the effect of the trailer tipping over.
If you look at the scene, the truck is also tipping, not just the trailer. Steering hard left with a truck and trailer on the verge of tipping to the right would increase the centrifugal force already acting upon it and it would have completed the tip over. Steering hard to the same direction of the tip while moving forward would apply the counter force necessary to allow the truck/trailer to return to normal center of gravity over the wheels. It is a physics error.
Plot hole: After McClane, agent Johnson, and Ferrell leave in the police car, Agent Johnson radios another agent to have DC police clear a path for them. Then on Gabriel's screen it says they have a voice match to Farrell. The problem is Farrell never said a word, so how would they have a voice match to him? Without the voice match they never should have found them.
Suggested correction: The agent says "Ferrell" over the radio which in turn gets picked up as a name match on Gabriel's screen as they were scanning for anyone using that key word. Not Ferrell's actual voice but anyone mentioning his name over the radio.
If it was just looking for anyone saying the word Farrell it would have been a "voice" match. A voice match implies but they got a match to Farrell's voice.
In this context it is a match on the name "Farrell" that was spoken, hence it is a "voice match." It's clunky but still works grammatically.
