As it entered the building, what remained of Flight 11 sliced through thirty-five exterior steel columns and heavily damaged two more. It severed six core columns and damaged three others. It shattered at least 166 windows. It broke the concrete floor slabs of the 95th and 96th floors eighty feet deep into the building. It launched a fusillade of flying debris that knocked or scraped fire-retarding insulation from forty-three core columns. It stripped the insulation from sixty thousand square feet of steel floor supports over several floors. It severed pipes that fed water into the fire
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