DESCRIPTION: The above photo shows a side-by-side comparison of the old windows just above the heliport tower and the renovation windows in the collapse zone. Remember the renovation line was just a few feet from the collapse zone. That is why you see fire coming through all of the windows north of the renovation line.

"The blast-resistant windows, installed on the outer E-Ring of Wedge 1, weigh 1,600 pounds each with glass that is an inch-and-a-half thick. The blast resistant windows sit within a web matrix of reinforced structural steel that is bolted to the slabs of each of the five floors. Stretched between the reinforced structure is a Kevlar-like, geo-technical mesh that, in the event of an exterior explosion, would keep debris away from personnel inside the building." Pentagon Renovation Website