On September 11, 2001, at 9:03 a.m., United Airlines Flight 175 crashed into the South Tower of the World Trade Center, striking floors 77 through 85. This occurred about 17 minutes after the first plane, American Airlines Flight 11, had hit the North Tower.
After the first plane hit the North Tower, many people in the South Tower began to evacuate on their own, despite an initial announcement on the public address system advising them to stay in their offices.
The impact of Flight 175 caused catastrophic structural damage and ignited a massive fire. The plane’s high speed and off-center impact left the building unbalanced and weakened the steel columns and trusses that supported the floors.
The crash and subsequent fire trapped hundreds of people on the floors above the impact zone. While one of the three stairwells in the South Tower remained partially intact, allowing some people to escape from above the impact zone, many others were unable to get out.
The fires, fueled by the jet fuel, weakened the building’s steel structure. As the steel began to heat up, the floor trusses started to sag, pulling away from the outer columns. This process, known as “creep,” eventually led to the failure of the core columns. The weakening of the steel structure caused the floors above the impact zone to drop onto the floors below, initiating a chain reaction of progressive collapse that led to the entire tower’s fall.
These rarely seen photographs taken by NYPD officer Walter Taylor before the South Tower’s collapse at 9:59 a.m. (56 minutes after impact) on September 11, 2001:
(Photos are from the September 11 Photo Collection Map, which is an exceptional resource. You can set the photographer filter to NYPD Walter Taylor for more photos and the location at which they were taken.)
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