It was the fire that killed the buildings
-- "structural engineer" Chris Wise; news.bbc.co.uk
New York Times reporters Jimm Dwyer, Kevin Flynn, and Ford Fesseden,
authored the series
Fighting to Live as the Towers Died
Glanz and Lipton went on to write
City in the Sky, which contains:
... on September 11 the columns of the twin towers really did shift load
around the dark, smoking holdes punched by the planes,
forming the arches and keeping the building standing.
Otherwise the towers would have crumbled in a heartbeat.
Many of those people saw and described
a structure in its final throes,
as floors began to buckle, heat rose, and
the building's defense systems failed.
Soon after Emery amd Gentul learned firsthand of
the building's failing vital signs,
their situation began to deteriorate.
About the same time, new fires broke out on parts of the ninety-third,
ninety-fifth, and ninety-sixth floors,
suggesting that whatever breakdowns had occurred inside were spreading
like a fatal malady to other parts of the structure.