What major global event occurred on September 11, 2001, in the United States?

What major global event occurred on September 11, 2001, in the United States?

Step 1: On September 11, 2001, a group of terrorists planned an attack.
Step 2: They hijacked four commercial airplanes.
Step 3: Two of the planes were flown into the Twin Towers of the World Trade Center in New York City.
Step 4: One plane was flown into the Pentagon, which is the headquarters of the U.S. Department of Defense.
Step 5: The fourth plane, United Airlines Flight 93, crashed in a field after passengers tried to regain control from the hijackers.
Step 6: The attacks caused significant destruction and loss of life, leading to a major response from the U.S. government.

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