Three Things You May Not Have Known About the WTC Twin Towers

1) They were built to withstand the impact of a 707, a plane about the size of a 767, but with four engines instead of two.

2) The Twin Towers were money losers-- they were not popular business sites, they were extremely expensive to heat and cool, and they required large subsidies to remain solvent.

3) The Twin Towers would likely have been demolished if not for the fact that they were filled with asbestos, and asbestos removal had to be done before the buildings could be demolished conventionally. However:

In 2000, the Port Authority calculated that it would cost $1 billion -- i.e., much more money than the Port Authority could afford to spend -- to remove the asbestos before the buildings were destroyed. And so the Port Authority was stuck with the Twin Towers, that is, until 26 April 2001, when it found a consortium of business interests (Westfield America, led by Larry Silverstein, the owner of the building at 7 World Trade Center) that was willing to lease the property.

(Larry Silverstein, of course, made a handsome profit on his investment from the insurance pay-out he received after 9/11.)