I was getting ready for my own flight that morning, had my suitcase packed and was arranging for transportation to the airport. I had set the radio to wake me up and it was still on at low volume in the background, too low to hear but loud enough that I could hear it was the news. I stopped and though, "wait, why is the news still on? Isn't after 9 o'clock? News should be done by now".
That's when I turned it up and heard about a mysterious crash at the North Tower, and in a few minutes the South Tower was also hit. I called my ride back and said, "forget about the airport, all flights are off --- we're under attack".
We went nowhere -- we sat in front of the TV the rest of the day watching in horror and trying to find out the fate of my flight attendant friend. That evening we were still watching the news from one of the networks, when the network signal simply disappeared. Vanished. I hadn't seen that happen in decades. It punctuated how serious the turn of events was.