My fiance (now DH) and I were out of town in FL for a conference I was at and we were flying home to DC that AM. Our flight never took off (it was grounded as we were to take off about an hour after the 2nd attack took place to by then they knew not to let other flights take off).
It was scary...we were just checking out of our hotel when the first flight hit the towers and they still thought it was an accident. I was at a gas station refilling our rental car to turn it in when the flight hit the Pentagon, I heard it on the radio and completed freaked out & started calling my friends at work (I worked in an office across the street from the Pentagon) and everyone was screaming and running downstairs evacuating their building

few there realized what had happened (other than the explosion at the Pentagon), although one person did actually see the plane fly into it, and b/c the military scrambled jets which were flying overhead at that point people running out of the office building actually thought we were being bombed by air as well.
Coming home is a whole experience in itself...we drove b/c no flights were being allowed anywhere near DC for weeks. The only people on the roads other than us coming up I95 were military caravans and tons of Red Cross & emergency responders. For my entire life I will never forget standing in the rental car depot (we had to rent a car to get home) with hundreds of first responders who had tons and tons of containers of body bags with them.
When we got home b/c we lived near the Pentagon & National airport we had to cross military roadblocks and prove our identity to get into our appt building. Same for me for months at my office, b/c we were next door to a number of Govt agencies so they kept soldiers w/AKA47 rifles at our entrances/exits.
I'm just thankful no one I knew was killed that day...I had a number of friends who actually worked at the Pentagon (both military & contractors) but they luckily weren't in the section that was destroyed.
Many thoughts today for everyone who was killed & their families still struggling with their loss. I cry to this day to think of the people on those flights & in NYC & the Pentagon...such a horrifying, senseless tragedy.