So where was the compression on flt 800?
PV=nRT
It was a hot day in JFK, the plane was delayed several hours on takeoff. The packs (air conditioning system on Boeing Airplanes) are directly below the center wing tank. The area became very hot.
That's why Boeing put an fuel tank inert system in the 787. There have been 4 center tank explosions.
http://en.wikipedia.org/wiki/Inerting_system