http://911research.wtc7.net/mirrors/guardian2/wtc/tower-explosions.htm The pancake theory would have the 98th floor collapsing onto the 97th, causing that to collapse onto the 96th, causing that to collapse onto the 95th, etc...
But a close look at the video/photos shows that the collapse begins at the 98th floor, then the 99th floor collapses onto the 98th, then the 100th floor collapses onto the 98th, then the 101th floor collapses onto the 98th, then the 102th floor collapses onto the 98th, etc until the second line of detonations initiates the final collapse. So once again, we have the disintegration of the tower above the impact floors, before the collapse of the tower below the impact floors.
Interestingly, this observation disproves the so called pancake theory, where one floor collapses onto the next lower floor, causing that floor to also collapse (not that the pancake theory made any sense anyway). Here, what we see is 5 or 6 floors in a row, all falling onto the 98th floor, which does not collapse (until the second line of explosives are detonated, taking out its support).