I had just returned from New York, the day before. I'd spent my last day there at the WTC, by chance. Ate in Windows on the World restaurant.
I was at my desk just after lunch time & a work friend rang me to ask if I'd been in WTC the day before. I said I had & then he said 'you might have been one of the last people to visit, a plane has just crashed in to it'.
I remember thinking what an odd over-dramatic thing to say, from someone not usually like that! Then found a TV in our boardroom & watched the 2nd tower being struck, and then seeing the 1st tower collapse ... I remember the utter shock.
Then I remembered my dad was still in NY so had a slightly nervous time until I found out he'd left NY about that time, one of the last trains to get out of NY, to travel to a work meeting.
Walking home that evening was surreal. It did feel like the end of the world, as others have said. Utter silence, no-one talking. Complete shock.
I will never forget the horror of seeing images of people at windows, stuck, then jumping out.
In Ireland we had a National day of mourning and masses were held everywhere. My dad was still in the States,, in Connecticut, but said everything had continued as normal there, meetings etc. No one was even talking about it. I suspect due to complete shock and possible fear about what it might mean.