Maybe, maybe not, but on the technical question of designing the building to withstand the impact of a 707, I have thought about this, and my theory is that maybe the structural engineers assumed the possibility of that size of jet "happening" to crash into the tower at a speed associated with that altitude, say 280K - 300K IAS max. When I saw the horrible TV images of the jets smacking into the towers, they appeared to be flying at max speed - I'm a 757 driver and I reckon they were on or beyond the "barber's pole" on the ASI i.e very fast. With a limited knowledge of physics, but enough to appreciate the significance of velocity in the E=0.5mvsquared formula, I reckon the velocity was too high for the structure to withstand, insofaras the jet penetrated so far in that the subsequent explosion and contained intense heat, weakened the vital strength and the kinetic energy damage combined to break the Camel's back.
My thoughts at this time are with all those who are suffering as a result of this tragedy, and I mourn the loss of so many fellow human beings.
I strongly believe that it will be a testament to their lost lives that we stand firm in our efforts to erradicate this threat to our civilisation, and continue to live our lives with hope for our future and that of our children. 2 days ago, the pendulum swung towards the forces of evil, many have said that the world is a changed place. I believe the overwhelming strength of good versus evil will prevail, but we must work hard to achieve it, and stand firmly together.