It doesn't have to be any thing other than a plane. Given the technology of remotely flying the planes is atleast 20 years old now, IF THEY EVEN DID IT, they really don't need to resort to painting something else as American Airlines plane.
Yes, I agree that the trajectory of the Plane that hit Pentagon is incredible. Making almost a 360 degree turn, while descending at super high rate of angle and speed, keeping the plane perfectly horizontal, almost PERFECTLY leveling at mere few feet from the ground, wings not even touching the ground...absolutely amazing... hard to believe the lone sanitary clothing head Hani Hanjour actually was competent enough to do that. But motivation can make people do impossible things. But I still do not rule out the possibility of remote controlled flying by rogue elements in the Gubmint. Just the unbelievable trajectory forces me to consider this possibility.