Regardless, in one of these small planes you have lots of time to decide where you are going, and I can't see any good reason why the pilot would hit the biggest building in town by accident. I have no idea if this was a terrorist attack or not, but if this was truly an accident the pilot probably needed help getting his shoes tied in the morning too.
patent
The structural "lesson learned" by terrorists on 9-11 is to hit near the top of a skyscraper to collapse it and get max return for your energy input. The low flat Pentagon was a "dud" strike by comparison.