Anachronisms

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).

Revealing mistakes

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.