Continuity mistake: When Harrison Ford tries to enter the conference room when he comes upstairs from the lower level, he first struggles with the guard to the conference room door. While fumbling with the keys, the guard "wakes up" and shoots 2 shots toward Harrison Ford, where he turns around and shoots back. Those 2 shots from the guard leave bullet holes in the conference room door. When Harrison finally enters the room, the bullet holes disappear. When the bad guys return, the bullet holes are gone.
Trivia: A little aside - when the terrorists first strike, in amongst the confusion you can hear someone shout "get the football!" The "football" is the name used for the case which contains the nuclear launch codes, but this is never explained. It's not a major thing, but interesting to note that they included it as a little detail. Good to know a childhood spent reading Tom Clancy books wasn't wasted...