I was scheduled to fly SNA-HOU that day to give a talk at an engineering show (ISA). When I was in the shower my wife turned on the TV and said ‘you’re not flying anywhere today’ - I didn’t believe that an event could occur that would close down the whole US airspace, so I told her not to be daft.
Well. We all know what really happened of course. I recall little for the rest of the day, only watching everything unfold on TV.