Due to the destruction of the gypsum-encased stairwells on the impact floors (most skyscraper stairwells are encased in reinforced concrete), no one who was above the impact zone in the North Tower escapes the collapse. The Marriott Hotel, located at the base of the two towers, is also destroyed. The second collapse is also viewed live on television and heard on radio. The North Tower collapses 1 hour, 41 minutes and 45 seconds after the impact of Flight 11.
