Factual error: In the beginning the guy shooting pool gives a CD to Richard Gere, he says that the song they were listening to is the fourth song when in fact it's the first song on the album.
Factual error: The geography throughout the film is all wrong. The setting is in Pennsylvania, near Pittsburgh. The driving times between there and Williamsport are extremely under-estimated. Most egregious is the river structure. The body is found in the river near Sunbury. Not possible from a site in Western PA. Basically all relationships between actual towns/cities mentioned are totally wrong.
Factual error: From the range that Snake fired his clip full of blanks at Malloy and his aide, they still would have been burned by the muzzle blasts and quite possibly deafened by the noise. They assuredly wouldn't have stood there smirking. (00:20:15)
Factual error: In the beginning of the movie, the explosion in the Holland Tunnel is caused when a car crashes into the trucks carrying toxic waste barrels. In real life, it is against the law for vehicles carrying hazardous chemicals to use any of the tunnels. Even if the drivers didn't know this, which is highly unlikely, they would have been pulled over by the Port Authority cops as soon as they headed for the entrance - lots of yellow barrels would be a bit suspicious.
Factual error: Toward the end of the film, Matthew McConnaughey is in his office late at night and hears someone outside (it turns out to be his wife). However, McConnaughey draws a revolver from his desk drawer and we can hear (but not see) him pulling the hammer back to cock the gun. Problem is: When pulling back the hammer on a revolver, the cylinder turns to rotate the next bullet into position. The cylinder did not turn. The sound we heard was obviously added by the sound editors after the scene was shot.
Factual error: When Smith shoots the first man with his twin .45s, the man flies back about 30-40 feet. In reality, he might fall back a foot or two, but he certainly wouldn't be propelled anywhere by simple bullets.
Factual error: In the bank robbery scene the signs in the teller windows say FIDC. The correct abbreviation is FDIC.
Factual error: We see John Cusack enter City Hall and turn right past the guard to meet Pacino, the Mayor in his office. In reality in New York's City Hall, the City Council occupies the right side of the building and the Mayor occupies the left side of the building.
Factual error: At the Oro Array, the breakers are turned off because the power is cut. When the alien cuts the cables to the computers, sparks fly out as if there is power.
Factual error: The movie takes place in 1925 but the uniform of the German fighter as well as the Zeppelin's markings are those of the Empire (gone 7 years ago).