I've been here all day, and I don't think anyone has posted about the drills. Very important information.
From 'Crossing The Rubicon':
"As it turns out, on September 11th, various agencies including NORAD, the FAA, the Canadian Air Force, the National Reconnaissance Office, and possibly the Pentagon, were conducting as many as five wargame drills, in some cases involving hijacked airliners, in some cases involving blips deliberately inserted onto FAA and military radar screens which were present during [at least] the first attacks; and which in some cases had pulled significant fighter resources away form the northeast U.S. on September 11."