From the report: > Despite simulating a number of hypothetical scenarios, we were unable to identify any progressive sequence of failures that could have taken

From the report: > Despite simulating a number of hypothetical scenarios, we were unable to identify any progressive sequence of failures that could have taken place on September 11, 2001, and caused a total collapse of the building, let alone the observed straight-down collapse with approximately 2.5 seconds of free fall and minimal differential movement of the exterior. Here's how: https://www.youtube.com/watch?v=JQPWpY24B0Q https://www.youtube.com/watch?v=JQPWpY24B0Q