Factual error: After the eastern hub explodes from the gas, and after Mathew's rant, McClane looks out over the city as the power goes out and all the lights begin to shut off. But all the headlights of the cars on the streets also begin to turn off, despite not being connected to the grid.brianjr0412
Factual error: They crash their BMW, and Doloris comes on in the On-Star system. On-Star has never been available in BMW vehicles, as it is a wholly-owned subsidiary of General Motors. BMW does offer a similar service called BMW Assist, but this was not available in any BMW model at the time of this movie.
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.
Factual error: In the scene where McClane jumps off the fighter jet he slides down at 100+ feet of highway concrete but when he reached the bottom his jeans are not torn in any new places. Any fabric rubbed against concrete for any significant distance would be shredded or (if conditions were perfect) at least frayed.