I remember it quite vividly too. I was 17 and watching the end of Neighbours (lunchtime ep), when the credits cut to the image of the second plane heading for the south tower, I saw it hit live, unbelievable!
I honestly thought they’d mistakenly put a disaster film on! It was so surreal!
I had been watching Neighbours too (

) and was probably waiting to watch Murder She Wrote or Diagnosis Murder but the news came on instead and me and my Mum just watched in disbelief it as it happened.
I was 18, so it was a pivotal time for me - finished college that June and had just started working full-time hours at the beginning of September (night shifts, hence me being at home in afternoon!). I just remember thinking nothing would ever be the same, I can't describe it very well...I suppose it was the first time I had watched* a major tragedy as it unfolded albeit via a television screen.
I think the first plane had already struck before the BBC broadcast began, but they were live when the second plane hit? Then the realisation that shapes falling were the people jumping, then the buildings collapsing....wow (in a bad way).
I went to work that evening and everyone - colleagues, customers - were all like, "did that actually happen?". A weird air.
The newspapers the next day...so many images that have stayed in my head, like the people just COATED in dust, and esp. the firefighter looking straight in the camera as he was going up the stairs as everyone else went down. I can't remember if he survived or not.
I know I wasn't there physically (not even in the same country). But I believe watching it as it happened has had a lasting effect on me. The world seemed more scary, more serious.
I always take a moment on the anniversary to remember all the people who lost their lives that day. I cannot believe it's been 20 years.
*the only other major event that had happened in my lifetime was Princess Diana's death but that didn't affect me half as much. And it wasn't a live broadcast.
(Coincidentally I was also at home on my day off when the London bombings happened, so watched that as it happened too

).