If you haven’t seen it, there’s an exhibit about 9/11 at the Smithsonian Air and Space Museum in DC that shows the airspace in the lead up to and just after the attacks. If you find the traffic changes now interesting, I think you’ll find that interesting as well. It’s possible it’s online if you do some googling

Appreciate that reference. I'll look for it.

The house where I lived on 9/11 is in the approach for a runway at a local airport. Air traffic was a fixture at that house. Somebody was landing at all hours most days.

It was the strangest thing to have no traffic at all back in 2001. It's odd for the absence of a thing to be jarring but it was.