sky9, you must not have read the linked article.
From the BBC...
The design of the World Trade Center saved thousands of lives by standing for well over an hour after the planes crashed into its twin towers, say structural engineers.
"It was the fire that killed the buildings - nothing on Earth could survive those temperatures with that amount of fuel burning," structural engineer Chris Wise
And from Engineering and News Record...
In the aftermath of the Sept. 11 terrorist attacks in New York City and Washington, D.C., which brought down the twin 110-story towers of the World Trade Center and damaged the Pentagon, designers and contractors say they are skeptical that signature structures can be hardened against extreme acts of barbarism.
"Only the containment building at a nuclear powerplant" is designed to withstand such an impact and explosion, says Robert S. Vecchio, principal of metallurgical engineer Lucius Pitkin Inc., referring to the hijacked Boeing 767 airplanes, heavy with fuel, that slammed into each WTC tower.