The document summarizes key details about the September 11, 2001 terrorist attacks in the United States. Four planes were hijacked by Al-Qaeda terrorists, with two crashing into the World Trade Center towers in New York City, one crashing into the Pentagon building near Washington D.C., and another crashing in a field in Pennsylvania after passengers fought back. Nearly 3,000 people were killed in the attacks, which were planned by Khalid Sheikh Mohammed and ordered by Osama bin Laden. The attacks significantly impacted the United States.