Final answer:
On September 11, 2001, al-Qaeda terrorists hijacked four planes, crashing two into New York's World Trade Center, one into the Pentagon, and one into a Pennsylvania field, resulting in nearly 3,000 deaths and marking the start of the War on Terror.
Step-by-step explanation:
On the morning of September 11, 2001, a major terrorist attack took place in the United States. Nineteen terrorists associated with the extremist group al-Qaeda hijacked four commercial airliners. Two planes were intentionally crashed into the Twin Towers of the World Trade Center in New York City, leading to their collapse. Another plane was crashed into the Pentagon in Washington, D.C. The fourth hijacked plane, United Flight 93, crashed into a field in Pennsylvania after passengers attempted to overcome the hijackers. The total loss of life from these events numbered nearly 3,000 people, including 400 emergency workers.
The 9/11 attacks had far-reaching consequences, marking the beginning of the War on Terror, which included military campaigns in Afghanistan and Iraq. The events of that day united Americans, instigating a surge in civic engagement, volunteerism, and military enlistment, reflecting both the resilience and the solidarity of the American people.