Since commercial jet-a, fuel doesnt burn unless under extreme pressure, why did it burn in the Trade Towers?

Commercial jet fuel, jet-A, will not burn except under extreme pressure found in the engines of the plane. So, given that an additive IS added to commercial jet fuel to frevent combustion except under controlled conditions, Why then did it continue to burn in the Trade Towers? Anyone who wants can verify my statement about Jet-A can check with the F.A.A., or the Department of Transportation. This seems awfully suspicious. I have also looked at several dvd's I own about Sept 11th, and a pod of some kind can be clearly seen on the bottom of the plane striking Tower Two, clearly marking it as a military plane. Plus, there are numerous witnesses who claim that the plane had no windows, was grey, not white, and had a blue circular emblem on the front of the fusalage, clearly marking it as United States Air Force.