"Keeping it going on a pre-set course might not be hard but turning a huge plane in midair and aiming it at a specific destination at 500 miles an hour might be just a tad more than I can handle."

It was probably more than the pilot could handle. From reports that are readily available online, it appears that the pilot was much too high to hit the target, so he made a 330 degree turn. However, it was not as if the turn was being made around the Pentagon. The turn was made in a rather wide circle and he came in to reach his target. It adds up to describe an inexperienced pilot who nearly broke the plane up with the stress that he put it under.