8:46:40: Flight 11 crashes at roughly 490 mph (790 km/h) into the north side of the north tower of the World Trade Center, between floors 94 and 98. The aircraft enters the tower mostly intact. It plows to the building core, severing all three gypsum-encased stairwells, dragging combustibles with it. A massive shock wave travels down to the ground and up again. The combustibles and the remnants of the aircraft are ignited by the burning fuel. Since the building lacks a traditional full cage frame and depends almost entirely on the strength of a narrow structural core running up the center, the fire at the center of the impact zone is in a position to compromise the integrity of all internal columns. Two home video cameras are known to have recorded the impact. People below the severed stairwells in the north tower start to evacuate; no-one above the impact zone is able to do so.
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