I did watch the footage as it was happening. Had the day off and sat with a friend horrified by what we saw.
Saw planes smack into buildings and the buildings collapse as a result. Don't know what gives you the idea I've been led by any government storys because honestly I've never seen the need to listen to any.
Smoke may not run down stairs but burning fuel or molten metal does fall down lift shafts.
Anyhow, I never sat down to get drawn into this. I read you ask about noises from the basement and thought I'd try to offer an explaination but now see it was a mistake.
As I said - feel free to disregard everything I've posted. I'll do the same and we can both go on our way believing what we believe. Have a good one.