Continuity mistake: Just before the guy crashes the plane into the towers, he reports his height as 1,300 feet. There is an almost instant look at the console in front of him and you can see the altimeter is saying he's at 700 feet. Whatever the hackers can change (they seem to change his GPS system reading) they cannot change this which relies on sensors mounted in the plane itself.
David Mercier
7th Dec 2004