Although fighter jets were airborne seven minutes after the first plane crashed into the World Trade Center, military officials received insufficient notice of the other hijackings to stop the planes, the staff statement said.
http://story.news.yahoo.com/news?tmpl=story&cid=615&e=1&u=/nm/20040617/pl_nm/security_commission_dc

The earliest notice the military had of any of the hijackings was nine minutes before a plane crashed.

At one point, unnamed senior FAA officials mistakenly directed Air Force fighter planes to chase American Airlines Flight 11, which had struck the World Trade Center's north tower 30 minutes earlier.

NORAD also said it was not alerted to the hijacking of United Airlines Flight 175 until after it hit the trade center's south tower.

FAA controllers lost track of Flight 77's route for 36 minutes. Once the agency identified an unknown plane "six miles from the White House," fighters were too far away to help, and Flight 77 hit the Pentagon (news - web sites).

"Sounds like we have a minor war going on here, I heard about the Pentagon. We're at war," President Bush (news - web sites) told Cheney. "Somebody's going to pay."

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The 9/11 report released Thursday methodically tracked the progress of the four hijacked airliners and matched that against a timeline of government response. The air defense of America began at 8:38 a.m. on that fateful day, notes the report, when the FAA's Boston center air-traffic-control facility notified NORAD's Northeast Air Defense Sector that American Airlines Flight 11 had been hijacked. Perhaps understandably, the first question asked by the Air Force personnel who received the call was whether the situation was "real-world, or exercise?"
http://www.csmonitor.com/2004/0618/p01s03-uspo.html

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The 29 page report said the White House was not informed of the hijackings until after the first plane hit the trade centre in New York.
http://www.abc.net.au/news/newsitems/200406/s1134534.htm

The investigators said previous procedures were based on assumptions the aircraft would not try to disappear, that there would be time to go through the proper chain of commands and the commandos would behave like traditional hijackers.