Just for fun Hans try listing the rreasons why the columns on the impact side couldn't have been replaced with lighter, weaker sacsimsiles or the originals just weakened. I mean only the sections in the impact area.
Sure:
1) Somewhat hard to hide. I mean you would have to expose the columns, flame cut them, lug tons of steel down to street level and drive it away, then hoist other structures back up ant put them in place. Would take an awful lot of green netting to hide that. (and there was no green netting observed at any relevant time)
2) Rather risky weakening a functioning building.
3) Too many people involved.
4) Impossible to predict the exact impact area. Flying aircraft into buildings is not a well-rehearsed procedure.
5) Quite unnecessary, since the impact of a large aircraft would be certain to make spectacular damage.
I'm not going into the fact that there is no sensible motive for such an operation, except for this: Somehow, Truthers seem to be stuck to the idea that the whole purpose was to have the buildings collapse. However, that was not necessarily the most desirable scenario, not even for the actual terrorists. Quite as efficient a horror would be achieved if they burned like torches for days, with the people trapped above the collision zones slowly frying or jumping to their deaths, with desperate cellphone calls going out from them. And afterwards, the US would have a couple of burnt out, unstable hulks standing as monuments of the event, till they could be, at great danger, demolished or taken apart piece by piece.
As it were, the worst was over in a few hours, and the clean-up operation could commence, heart-breaking as
that was.
Hans