Prelude 9/11 morning Flight 11 hijacked Flight 175 hijacked WTC 1 hit Flight 77 hijacked WTC 2 hit Flight 93 hijacked Pentagon hit WTC 2 collapses Flight 93 crashes WTC 1 collapses WTC 7 collapses Epilogue

FEMA (response)

Prior to September 11 2001, there were no clear procedures on which government body was in charge when a building collapsed. Following the attack, the American Society of Civil Engineers, the American Institute of Steel Construction, the American Concrete Institute, the National Fire Protection Association, the Society of Fire Protection Engineers, and the Federal Emergency Management Agency (FEMA) joined forces and launched an independent investigation of the event.
The resulting report was published in May 2002, but was criticized for not being sufficiently thorough. Thus, the National Institute of Standards and Technology (NIST) declared that they were launching an investigation of their own.

The FEMA report should be regarded a provisional explanation of why all buildings in the World Trade Center complex were destroyed.

FEMA 403: World Trade Center Building Performance Study

This is the full report (298 pages).

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