Reply #57: So The hijackers had to aim for specific floors?

[Taxloss]

And arrange where the explosives were placed to appear correct? And this would be judged by sight, from a speeding jet? And the explosives were set up without office workers on those floors noticing? And they were certain the explosives and there trigger mechanisms would survive the impact and a drenching from burning jet fuel and whatever other plumbing was broken?

Or were the explosives on those floors just by happy chance? Or were they placed on several floors?

An explosive shockwave at the core would resonate the entire building. Buildings, all buildings, are covered in loose filth, especially if they've just been showered in ash and debris. That would be clearly witnessed as a wave passing up the building.

Part of the preparations for a controlled demolition is to remove all the windows, because they will almost inevitably blow out wherever the explosives are placed, scattering broken glass. This did not happen on the lower floors.