I was in the US, in suburban Chicago.
DD4 was exactly three weeks old that day. The oldest three DCs were in school and DD3 was at home with me and my mum, who had flown from Ireland to help out when DD4 was born. It was a sparkling September morning. School had been back since just after DD3 was born. Mum had walked them all to school along with DD3 and they had played for a little in the park on their way home.
The incredible tiredness of the newborn phase had hit me and I was having a lie in when my mum came to my room and said something had happened in NY and all the TV stations had started coverage (she had made a cuppa and was watching TV with little DD3).
I got up to see and had just settled on the couch when the second plane was spotted and of course it slammed into the second tower.
We tried phoning my cousin in NY but phone service was cut off in lower Manhattan, so we didn't know if he had been injured, trapped in his home or at work, or what. We had to phone mum's sibling in London for news - cousin was fine, was on vacation away from NY at the time. We were so relieved.
A little later there was news of the plane coming down in a field in Pennsylvania, the plane hitting the Pentagon, footage of George W. Bush in the Florida school being told the news, and news that Air Force One was in the air heading for some secret location. It was all very dislocated.
Mum guessed immediately that they had hijacked planes heading all the way from Boston to LA to maximise fuel.
Then the school phone tree sprang into action with notification that the school would close for the day at lunchtime, and mum went off to pick up the three oldest DCs. Commuters were streaming home from the city, train after train and car after car. The city emptied in the space of a few hours. The DCs had heard the news at school and had said some prayers in their classrooms (RC school). I made lunch for DD3, who was delighted that everyone was home early.
Planes were grounded and the highways were empty. The usual background buzz went completely quiet. We heard the occasional Air Force jet overhead but most of the planes we saw were miles up and we heard nothing.
Mum realised she was stuck in Chicago for the foreseeable - she had been due to fly back to Dublin the following day but she ended up staying another week. She really had ants in her pants by about day five of her bonus week...
When she arrived home and unpacked she realised that she had inadvertently packed a roll of packing tape with a built-in 2 inch blade in her carry-on luggage, but it wasn't spotted by the 'new, improved' security, despite the fuss about prohibited items and having to leave several personal items behind as they were verboten.