Plane at State of Union address

What if those terrorists had used a plane to hit the U S capitol during a January State of the Union address? With all those members of Congress present with the President, VP, et al, much more damage would be done, wouldn't it? Then, those reprobates are pretty useless.

they would not let a plane near there during that time...

Nah, they would have been evacuated and spread out. Some may die, but they'd get them seperated very quickly.

Read Debt of Honor by Tom Clancy. Ends with basically the same scenario you just described. From what I understand, the US government brought Clancy in as a consultant due to him writing about that - they wanted to see what other ideas he had that could help forecast what terrorists would do.

In an event like that, all three branches of the government would be crippled, but continuance of government plans ensure that there would still be leaders to help restore the government.

Also, as spangbr said, the airspace over the capital is very tighly controlled during a SOTU address, or similar event. Even before 9/11, a plane would be shot down if it got too close - I've heard rumors about Secret Service agents on top of buildings in DC with Stinger missiles, and I'm sure after 9/11 there are fighters guarding the airspace.