The Commerce Department's National Institute of Standards and Technology (NIST) recently presented its analysis of how the World Trade Center (WTC) towers collapsed after two aircraft were flown into the buildings by terrorists on Sept. 11, 2001. This is the most detailed examination of a building failure ever conducted.

The probable collapse sequences, which update and finalize hypotheses released by NIST last October, were presented by WTC Lead Investigator Shyam Sunder at a press briefing in New York City. Sunder also released drafts of 15 reports from three projects of the investigation: Analysis of building and fire codes and practices; occupant behavior, egress and emergency communications; and fire service technologies and guidelines.

Recommendations from these projects, as well as all other projects in the investigation, will be released for public comment in June.

The news release detailing the briefing may be found at this link.

All materials related to the announcement, as well as background and archived information on the NIST WTC Investigation, may be found at