this article has two interesting things

1) F-16's ofen follow commerical airlines not to protect them 
   but so they can shoot them down if they think terrorists 
   might hijack them. yea sure i have lots of faith in the 
   government us from terrorists.

2) terrorists if they hijacked ONE plane might be able to crash 
   it into the white house before F-16's could shot it down, BUT
   if they hijacked SEVERAL planes they almost certainly could 
   crash them into the white house before fighters got a chance 
   to shoot them down. well i guess the goverment protects the
   president and the rest of our elected royality much better 
   then it protects us peons.
  

http://www.azcentral.com/arizonarepublic/news/articles/0116airterror16.html

Washington airspace remains at risk of terrorist penetration
 
John Solmon
Associated Press
Jan. 16, 2004 12:00 AM


WASHINGTON - U.S. and Canadian military aircraft have scrambled nearly 1,700 times to intercept or divert suspicious aircraft since Sept. 11, but routine drills illustrate how terrorists could penetrate the airspace around the nation's capital, officials said this week.

"We do these tests to push the system, find holes, and when we find holes we correct them," said Canadian army Maj. Douglas Martin of the North American Aerospace Defense Command. 

"Every time we do a test or an evaluation or exercise, we're getting better at defending the national capital region," he said.

Officials said the exercises conducted in early and mid-December are the latest to show that the best prevention against another terror tragedy in the skies is thorough pre-emptive intelligence and screening, not a last-minute intercept or shootdown of a hijacked commercial airliner.

Those officials talked to the Associated Press about the classified results of the drills only on condition of anonymity. 

They said U.S. military officials have concluded it would be very difficult to intercept a hijacked plane within a certain radius of major cities like Washington unless fighter jets were already airborne.

Possible airline hijackings were a major concern around the New Year's holiday, when nervous U.S. officials caused a number of international flights to or from Washington and Los Angeles to be canceled or severely delayed. F-16 fighter jets reportedly escorted some flights as they approached U.S. airports.

In some of the tests in December, officials withheld fighter jets in order to check other last-resort defenses around the capital such as ground-to-air missiles and artillery, Secret Service protection and Federal Aviation Administration communications, the officials said.

The officials declined to provide more specific details about the drills except to say that under some circumstances Homeland Security planes posing as mock terrorists were able to penetrate protected air space.

The officials declined to define the zone in which scrambling military jets become ineffective although they noted the government typically creates a buffer of just over 30 miles when setting up temporary protected airspace around special events or presidential locations.