A plane with a bomb that exploded after impact makes the most sense. Fits with the witnesses "thermite" description and the ones that saw a plane.
With such a gigantic planned deception like that one it isn't unreasonable to suggest a small plane carrying damaged 757 parts to plant evidence.
Whatever the case the official version is the fantasy.
Here's another bit to argue...
http://www.mycountryrightorwrong.net/F-15.htm
... ever notice the flash of fire before the plane hits the WTC, or the black streak in the sky. If you'd taped the TV coverage watch it again for both of those.