Does anyone remember the 1974 movie called "The Towering Inferno". the similarities are amazing!
Go HERE to visit a site with tons of pictures that look just like the World Trade Center! Another good link is HERE.
The very week prior to 9/11, Les Robertson, the Professional Structural Engineer in responsible charge of the design of the WTC Towers said to an anti-terrorism conference regarding his building design "I designed it to withstand a 707 flying into it."
Maybe you didn't consider it, but I'm sure the designers and insurers did. Planes flying over NYC have hit other buildings and even each other before. Obviously this is something to be prepared for, even if only as an accidental incident.
Finally, Ramzi Youssef, mastermind of WTC attack #1 in 1993 was caught with plans to comandeer a plane and fly it into the CIA HQ in Langley. Tom Clancy had written about a fictitious terrorist plot to fly a plane into the Capitol. The use of planes as weapons is as old as the Kamimaze attacks.