I had just finished ASTC school at Lemoore NAS. After a long period of no downtime, I flew to Hawaii for a dive vacation on the 9th. On the 11th, my girlfriend at the time, who lived in DC, called me at zero dark thirty HI time and told me to turn on the TV.
It was surreal to me just because with Hawaii being so far from the mainland made it feel like I was watching something happening in another country. There really wasn't much change from business as usual in Hawaii. The dive outfit still went out that day, and everyone went on with their business. Almost like when you read about "3000 people die in an Indonesian earthquake". You recognize it, but it doesn't really affect you.
The one thing I will always remember is the quite from the flight restrictions. Hawaii has a constant background noise of aircraft flying into the various islands. You don't notice it until it's not there. The quite of no planes in the sky for the rest of my leave, other than a couple of military aircraft, was simply eerie.
Air travel opened up one day before my scheduled departure. The other thing I remember thinking about was what if I was stranded in Hawaii? The air restrictions could easily have gone on for longer, or the attacks could have been even worse or more widespread, and I would have been across an ocean from home (versus being stuck 1000 miles from home on the mainland, where alternate transport or even, worst case, walking might be options). It might have been something my credit card could have solved and just turned into a longer vacation, or infrastructure could have gone down and I would have been stuck with whatever I brought with me in my duffel bag. It definitely made me rethink my SHTF scenario for all future trips.