On September 11, 2001 at 8:46 a.m. Eastern Time, Al Qaeda suicide hijackers crashed American Airlines Flight 11 into the northern facade of the North Tower. Seventeen minutes later, at 9:03 a.m., a second team of hijackers crashed United Airlines Flight 175into the South Tower, which collapsed and disintegrated at 9:59 a.m. At 10:28 a.m., the North Tower collapsed and disintegrated. At 5:20 p.m., 7 World Trade Center collapsed due to uncontrolled fires causing structural failure. 3 World Trade Center, a Mariott hotel, was destroyed during the collapse of the two towers. The three remaining buildings in the WTC plaza sustained heavy damage from debris, and were ultimately demolished.

At the time of the incident, media reports suggested that tens of thousands might have been killed in the massacre, as on any given day upwards of 50,000 people could be inside the towers. Ultimately, 2,749 death certificates were filed relating to the 9/11 attacks, as of May 23, 2007. Of these, 1,614 (59%) were identified from recovered physical remains. 343 of these deaths were New York City Firemen, 84 were Port Authority Employees, of whom 37 were Police. Another 23 were New York City Police. Of all the people who were still in the towers when they collapsed only 20 of these people were pulled out alive. Morgan Stanley was the largest tenant in the World Trade Center, with approximately 2,500 employees in the South Tower and 1,000 in the North Tower. For the following 8½ months, the World Trade Center site cleanup and recovery continued 24 hours a day and involved thousands of workers. The massive pile of debris smoked and smoldered for three months.

World Trade Center attacked