The documentary by the Naudet brothers is an unbelievable real time account of 9/11. I’m not actually sure how well known it is as I only saw it recently.
Two French brothers were filming a documentary with a fire department when it all kicks off. Pretty sure that’s the only footage of the first plane hitting. One of them films from inside Tower 1 when Tower 2 collapses it’s like something from a film.
It’s on YouTube, obviously heavy going but it’s surreal.