The only time I saw it was the evening of 9/11, they showed it twice on Fox and I've never seen it since in any documentary or commemoration. The camera view was literally looking straight up at the second plane exactly where it hit.
I knew a guy who was a firefighter in the station across the street from the twin towers who responded to the parking garage bombing that happened a few years before 9/11. He told me that over 50,000 people worked in each of the towers at that time, and with visitors and people doing business there could be up to 100,000 people in each building.
Thank God bin Laden came from Arabic culture, their business day starts and ends much earlier. If he had attacked at mid-afternoon instead of the beginning of the day the casualties would have been in the hundreds of thousands.