On the morning of September 11, 2001, an estimated 17,400 people were present in the Twin Towers of the World Trade Center complex. Estimates of the number of people typically in the Twin Towers by 10:30 am range from about 14,000 to 19,000, with turnstile counts indicating 14,154 as a typical figure. The National Institute of Standards and Technology determined approximately 17,400 civilians were in the World Trade Center complex at the time of the attacks. More specifically, it is estimated that between 1,344 and 1,426 people were in the floors 92–110 of the North Tower when American Airlines Flight 11 crashed, none of whom survived. Around 599 to 690 people were present on floors 77–110 of the South Tower when it was hit by United Airlines Flight 175, with only 18 survivors. Overall, the number of people in the Twin Towers at the time of the attacks is estimated to be around 17,400, though precise counts are difficult due to the chaos of the event and multiple sources of data.
