Terrorists associated with the al-Qaeda network led by Osama bin Laden hijack four airplanes. One crashes into the Pentagon in Virginia; two crash into the twin towers of the World Trade Center in New York City; and a fourth plane, believed to have the White House as its intended target, crashes in a field in central Pennsylvania. All told, more than 2,700 are killed. Afterward, federal agents take more than 1,200 people into custody. Most of the detainees are held on visa or other immigration violations and are not charged on terrorism-related offenses.