Maybe so, but face it, if the scenario I described happened, NOONE would be in the WH for years. It would have to be literally removed and replaced. As might dozens of other nearby buildings. Not to mention the panic across the nation and damage to the economy. Of course, the WH and DC is mainly a symbolic target.Yet symbolism seems to be important to the Islamofascists.
If terrorists really want to do damage they don't need a plane. A suicide bomber would walk into Grand Central, or Times Square and contaminate the most expensive Real Estate in the US.
Of course they can. So live the best you can.