You're correct mostly. They can bring any aircraft down quickly, like they did with Flight 94. I won't expand on that, except to say we have many options, and most of them include changing the aircraft from something with lift to something that more resembles falling metal, without the need for big explosions/burning/melting etc. [be creative] If any aircraft vectored funny and didn't follow commands, it would have fallen from the sky before hitting that school. Fighter Jets which are always on standby to interdict military aircraft, OTOH, were issued stand down orders by the War Games Command prototols. Pilots verbally, repeated opening of function but were refused by none other than Dick Cheney. [This particular item is documented in Congressional Testimony by a FAA rep who was present] So to follow up on that, SS and others don't participate in those drills 'in situ' they are always on duty. So that airspace around Bush was covered quite well by various means without prohibitions on using their weapons.  tldr; The Air Force or Navy could have easily shot down any aircraft that entered W's airspace, even though they were prohibited from engaging other aircraft that day [Except Flight 94] due to War Games going on.