Retired F-16 fag here. Had to be a plane we have the radar ground-track, it pulled heavy G's in a descending turn which means it had wings. They convert old fighter jets into drones all the time.
"yeah but thats a reinforced hardened structure aluminum at speed wouldnt do that im talking plate glass steel reinforced lower to the ground built into a platonic solid lack of better words a fortress"
Think kinetic penetrator, it's not the material it's made of, it's mass and velocity, it was exceeding 757 Vne, like Mach .9+
The hole in the Pentagon before portions collapsed after burning for a while was less than 10ft in diameter, but the penetration was deep
Besides, F-16s are made of titanium, not alu.
All that really matters like Jonathan says, is that it wasn't a hijacked airliner.
Photo, QF-16, optionally-piloted target drone. They've been converting fighters into missile-training drones since the 60's, there are a dozen easy candidates for the aircraft they used to hit the Pentagon.
Of course the only thing we really need to know, is that the freaks were out in force immediately, confiscating all the security-cam footage with a view of the flight-path, which they refuse to release.
Which means the confiscation teams were already standing-by, and they knew what the flight-path would be.
..including which cams could see it, which means a serious ground recon and inventory of all the cams in the area, and field-of-view analysis prior. That took a dozen guys a month or four to pin-down.
That is why the drone descended steeply, in a tight turn, to minimize the number of cams that would see it. The easiest flight profile for the attack would have been straight-in. However that would have guaranteed random video evidence like dash-cams etc.
Serious trick, piloting a vehicle at .9 Mach in a descending turn to precisely hit the place in the Pentagon where all the financial records of Cheney's Missing Trillion$ were placed for the attack.
Which pretty much rules-out a cruise-missile or a regular drone, and points to the QF-16 pictured above. Either that or a Navy F-18, but we know USAF NORAD was in on it, not the Navy. So, USAF QF-16.