A friend once asked me what I remember about nine-eleven; my answer was right on the tip of my tongue.
Planelessness and silence.
They say there are things you don't notice until they're absent - it was that way for me with the airplanes. I'd gotten so used to the contrails in the sky, the sounds of jet and propeller engines overhead, that when they were all grounded their absence was, well, spooky.
You might imagine that those sounds would be muffled by distance, or overtopped by the sounds of cars and trucks on the road. But for the days that followed nine-eleven, it seemed to me as if the entire mechanical world was muffled.
As if my entire neighborhood - and maybe the entire nation - was holding its breath, waiting for ... whatever.