These people are crazy enough to do that ... put biological weapons on board the airplanes that would be released upon impact.
Another thing I've thought about is this: Don't airlines come from countries that are hostile to us? I mean, what if a middle eastern airline which is destined for US has a nuclear warhead planted on it and the pilot is one of these terrorists? Couldn't they just plow into the white house or any target they choose?
I am beginning to get scared. Am I overreacting?