NORAD claims that after being told of the hijacking at 8:40, it waited six minutes to give the scramble order to the Otis pilots. It then took another six minutes before the pilots took off. So, at 8:52, two fighters took off toward New York City. According to Lt. Col. Timothy Duffy, one of the pilots, before he took off a fellow officer had told him, "This looks like the real thing." Duffy later said, "It just seemed wrong. I just wanted to get there. I was in full-blower all the way." A NORAD commander has said the planes were stocked with extra fuel as well. [Aviation Week and Space Technology, 6/3/02] Full-blower meant the fighters were going as fast as they could go. An F-15 can travel over 1875 mph. [Air Force News, 7/30/97] Duffy later said, "As we're climbing out, we go supersonic on the way, which is kind of nonstandard for us." Their target destination was the airspace over Kennedy airport in New York City. [ABC News, 9/11/02]
So even if the late notification of 8:40 is true, these fighters still should have been able to reach New York City before Flight 175 as long as they traveled 1100 mph or faster - far below their maximum speed of 1875 mph. In fact, Major General Larry Arnold says they did head straight for New York City at about 1100 to 1200 mph. [MSNBC, 9/23/01 (C), Slate, 1/16/02]
Yet, according to NORAD, the journey took 19 minutes, meaning the fighters traveled below 600 mph, and below supersonic speeds. [NORAD, 9/18/01] Major Gen. Paul Weaver, director of the Air National Guard, thus made the absurd statement, "The pilots flew 'like a scalded ape,' topping 500 mph but were unable to catch up to the airliner." [Dallas Morning News, 9/16/01] At that speed, Flight 11 would have been traveling faster than the fighters!
source