9/11 is one of those horrible things you remember where you were and what happened and you never forget it. I also remember the JFK assassination and I was a little kid when that happened. In the case of 9/11 I'd just gotten home from work [yes, I worked nights back then]. I turned on the news and an airplane had just hit the WTC. I noted it was a clear day and figured that had to be some sort of terrorism. As I was watching this, Wham, a second jet hit the building. Well that kind of removed all doubts. Anyway, you don't forget these kind of things.
I don't have anything to add.