
It is often said that the 1993 WTC bombing was under the north tower and threatened to take the tower down. This is a myth.
The fact is that the bomb was in the parking garage under the Vista Hotel (WTC3) and did only superficial damage to the tower structure.
Popular Mechanics (July 1993) shows a diagram of the damage, which was outside the footprint of the North tower.
http://books.google.com/books?id=pOMDAAAAMBAJ&pg=PA40&lpg=PA40&dq=popular+mechanics+1993+world+trade&source=bl&ots=rJppu41…
As you can see, the bomb damaged the refrigeration plant on the B5 level, which was outside the perimeter wall of the North tower.
Take a look at the strength of the tower during construction. How could this small bomb affect its overall integrity?