The 9/11 incident refers to a series of coordinated terrorist attacks carried out by al-Qaeda, an Islamist extremist group, on the morning of September 11, 2001. Nineteen terrorists hijacked four commercial airliners scheduled to travel from the East Coast to California. Two planes were flown into the Twin Towers of the World Trade Center in New York City, one plane was flown into the Pentagon in Virginia, and the fourth plane crashed into a field in Pennsylvania after passengers attempted to retake the plane. The attacks claimed nearly 3,000 lives and injured thousands more. The events of 9/11 were the deadliest terrorist attacks in American history and had a catastrophic impact on the country and the world. The attacks led directly to the US declaration of the "War on Terror" and subsequently later to the invasion of Afghanistan and Iraq. The tragedy of September 11, 2001, will never be forgotten, and the aftermath is still continuing to unfold.