Skip to 1:50 in the video and watch the collapse of the tower. You will see to the right a flimsy facade for 15 seconds.
While browsing news coverage of 9/11 on YouTube, I came across an interesting vid caught live as it happened of the north tower's collapse. As you may know, in some photographs and footage, a supposed remnant of the core column is standing even after the collapse. I believe that the remaining part of the building was an exterior portion. What caught my eye here was that this is the first time I have seen footage of that remaining section stay up for that long.