I remember it quite vididly. I was flying from Grand Forks (GFK) to MSP. I was flying myself solo in a C-172. I literally took off 5 minutes before the ground stop was put into place across the country.
Since it was a beautiful day I was flying VFR, and as soon as I took off and said goodbye to Grand Forks tower I switched the radio to some random frequency. Didn't want to have to listen to all the traffic in the area. For those that don't know the airspace around GFK is really busy due to University of North Dakota's (UND) commercial flight bachelor's degree program. UND has a fleet in number's that at that time was equal to or greater then most commercial airlines. (This was of course pre-merger so airlines on average had half the fleet they have today)
After turning the radio, I selected direct on my GPS, set the autopilot, and planned on an uneventful flight down to MSP. However about 1 1/2 hours into flight the frequency I had randomly tuned to picked up some guys on the ground talking. They sounded drunk, and what they were saying just reaffirmed in my opinion that they were drunk despite the hour. They kept going on about how the FAA had shut down US airspace. Then they started to talk about the Air National Guard in Fargo being deployed to DC. I again still thought they were just two guys drunk talking on a ground radio.
About 15 minutes later as I'm looking out the window I see one of the Fargo fighter jets flying in the distance. (He didn't come towards me, just got close enough I could see him and his friends in the far distance). At that point the guys continued to talk, and now seeing this I decided they might not be as drunk as I think. However I still don't think the FAA has closed airspace. I decided then to dial up Princeton Flight Service Station (they're the FSS for MN). Dial them up, and tell them I'm hearing some guys talk on the radio, and is there anything going on.
It was at that point that Princeton FSS delivered the order to land. Very clear cut "By order of the Administrator of the FAA you are ordered to land at the nearest suitable airport." I of course inquire as to the reason, they replied simply with the same line as before refusing to say why. At this point I open my airport facility directory and begin searching for an airport to land at.
While I had already past it, I decided back tracking about 15 minutes would be the best place to land. I ended up diverting to Detroit Lakes, MN. When I landed the local FBO operator came out to great me. He was actually quite shocked someone was still in the air. I got inside and called Princeton FSS and informed them I was on the ground, and that they could close my flight plan. It was then they informed me I was the last flight up in the air in NW MN and NE ND. Since I had filed a flight plan they knew who I was and where I was going. However they informed if I hadn't (filing one is not required for VFR flights, however offers the protection of someone searching for you if you don't arrive on time) that I would have received an escort until landing. At this point I still had no idea what had happened.
Finally after closing the flight plan I turn around and see a TV. On it is the images of the WTC being hit and collapsing. I actually had a slight sigh of relief I had thought someone had finally lost it and launched a nuke and taken out part of the country. The order to close US airspace had never happened, in my mind a nuke was the only thing I could think of that would cause such an order. Of course that sense of relief only last about 1/2 a second before pure anger and grief hit. I have family in NY and DC. I had actually been at the WTC only two weeks before with family. I also have many friends and family in the aviation business, and family in the NYFD. Luckily none of them had been hurt, and all were like me stuck at various locations. I of course canceled my appointment in MSP, and after realizing that commercial much less general aviation wouldn't be taking off for a few days went about securing a way home. Detroit Lakes has Amtrak service, but when I contacted them I found out the trains had already filled up for at least a week out. Finally I went about seeing if there was a rental car company I could one-way from. Of course Detroit Lakes is small and has no major car rental companies. The only rental cars were those the local Ford dealer rented out. I called them up, made a reservation with plan to return in a week, and asked to be picked up.
Got to the Ford dealer. They asked for credit card, ID, and type of vehicle wanted. I had over my ID and credit card. She then looks at me and says, I'm sorry you're only 22 we don't rent to anyone under 25. I look at her, point out I'm stuck here because I was flying and forced to land here. She wouldn't budge. Finally a manager senses my frustration and comes over to see what the problem is. I calmly explain that I was flying from GFK-MSP and was forced to land here in Detroit Lakes due to the FAA order. He then looks at her and in one of the more memorable lines that day says "Look he just rented a $200,000 plane, was flying over our heads, and was forced to land here, I think we can safely rent him a $10,000 car." She was pissed, but of course had to proceed to rent the vehicle to me. In the end the manager ended up being extra nice and instead of some small car gave me a F150 full cab.
Five days later with no end to the general aviation ground halt I made plans with a friend to return the truck. However that very night they lifted the GA ground halt. I called the place I rent the plane from and inquired if it had been picked up. They told me no. I told them great, then I'll return the car and fly the plane back in the morning. Of course nothing works out that well. I get back down to Detroit Lakes, return the car, get dropped off at the airport, and ask the FBO to pull the plane out so I can return it. He looked at me funny and then explained that the FBO I had rented it from came down that morning and flew it back!! I had to call the rental FBO and ask what the heck happened. The main pilot wasn't sure what had happened, as far as he knew the plane was there and I was to fly it back. Apparently that morning one of the companies pilots saw the ground halt had been lifted. Deciding to get some brownie points without informing anyone he had another pilot fly him down and drop him off. He then picked up the plane and flew back. Since no one was renting the plane for a few days he went ahead and hangared it, thus the chief pilot not knowing it was back. He of course offered to have someone fly down and pick me up. About the only problem with that was having to waste a few hours in an airport with nothing to do, no laptop, no books, etc. In the end I did of course get back home.