[mhays]

Originally Posted by marshall

The Twin Towers were designed to withstand the collision of the largest commercial jet in existence as of the 1970s, a 707 I believe. Of course, the caveot to this was that it was thought that any such collision would be due to fog, or technical problems with the plane either coming in for a landing or taking off, etc. It was never thought that a jet loaded with fuel would speed into the towers deliberately, and at such a high rate of speed so as to do severe, irreversible structural damage. Similar to your question, I also wonder if one of the South Tower collision had been averted, and only the North Tower had been hit, might the South Tower had survived the North Tower collapse?

747s were developed in the 1960s and (per wiki) first flew commercially in 1970.