True but if you look what Les Robertson has said is that they studied the impact but didn't take into account the fuel load and its effect, and what the fire damage would do.
Page 31 also talks about the bomber that struck the Empire State building and why it was completely different from the World Trade Center.
You should actually read the whole article, it does an excellent job of refuting the bomb theories and demolitions theories.
page 31
http://books.google.ca/books?id=3C7J...age&q=&f=false