World Trade Center site
On the morning of September 11, 2001, Islamic terrorists affiliated with Al-Qaeda hijacked American Airlines Flight 11 and United Airlines Flight 175, both which were en route to Los Angeles, and intentionally crashed them into the two main towers of the World Trade Center. The towers collapsed within two hours of the collisions. 2,606 people, including 2,192 civilians, 71 law enforcement officers, and 343 firefighters, who were in the towers and in the surrounding area died in the attacks, as well as 147 civilians and the 10 hijackers aboard the two airliners. After the collapse of the World Trade Center, hospital workers and law enforcement officers began referring to the World Trade Center site as "Ground Zero".
Hijackers in the September 11 attacks
According to the 9/11 Commission Report, 26 al-Qaeda terrorist conspirators sought to enter the United States to carry out a suicide mission. In the end, the FBI reported that there were 19 hijackers in all: five on three of the flights, and four on the fourth. On September 14, three days after the attacks, the FBI announced the names of 19 persons. After a controversy about an earlier remark, U.S. Homeland Security Secretary Janet Napolitano stated in May 2009 that the 9/11 Commission found that none of the hijackers entered the United States through Canada.