It's hard to say what hit the building since the video footage that we have isn't very good. The things that are odd about it are the angle of attack. It was flying really low to the ground which is odd. The object performed a really difficult maneuver before it hit the building. The pilot was untrained as well. It's an extremely unlikely event for it to hit the way it did but it's still plausible for it to be a plane.

The place it hit in the pentagon was investigating $2.3 trillion of missing money and the backup for the data was held in WTC 7. WTC 7 also just happened to fall due to office fires. Now that's what I find to be an unbelievably coincidence.