Collapse of South Tower - skip to 2:38 for clearest footage.
Note how the top floors of the tower fall to the side and away from the lower floors.
Official explanation is that floors above impact zone collapsed straight down into lower floors and into footprint of building.
But if the top floors collapsed to the side then what created the mass or force required to collapse the lower floors down to street level in seconds?
The only other possible explanation considering that the video footage debunks the official explanation.
9/11 wasn't a perfect op. The big mistake was made by the black hat drone operator of UA 175 (unlikely that they had a pilot flying on board), he failed to strike the center of the South Tower. Hitting at an angle caused the sideways collapse.
The other drone operator struck the center of the North Tower for the cleaner demolition.