NIST's official account (NCSTAR 1, Oct 2005; FAQ): WTC 1 (hit 8:46, fell 10:28) and WTC 2 (hit 9:02, fell 9:58) collapsed because the impacts severed columns and stripped fireproofing, and multi-floor fires (up to ~1,000 °C) made floors sag and pull the perimeter columns inward until they buckled. The upper blocks then fell 'essentially in free fall'. 2,735 died at the towers. NIST says it did **not** test steel for explosive or thermite residue, arguing thermite burns too slowly and the evidence didn't call for it. WTC 7 (fell 5:20 pm, not hit by a plane): NIST (Nov 2008) found fire-induced thermal expansion failed column 79; after public challenge (Chandler), the final report acknowledged ~2.25 s of free-fall acceleration. The UAF/Hulsey study (2020, funded via AE911Truth) concluded fire did not cause WTC 7's collapse. The separate, documented handling layer: 'the 28 pages' on Saudi support for hijackers were classified until 15 Jul 2016, and the FBI's Operation Encore (Bayoumi) summary was declassified only in Sept 2021 under EO 14040.