powerful country like the United States could be a victim of terrorism. But the horrific event also brought Americans closer together. As U.S. senator John Kerry said at the time, “It was the worst day we have ever seen, but it brought out the best in all of us.”

dark smoke poured from the twin towers. People rushed to escape the area, which later became known as ground zero. First responders—including police officers, firefighters, and paramedics—arrived within minutes of the first attack on the World Trade Center. They rushed into both towers to help people trapped inside, even though it would be an extremely difficult rescue operation. Almost all the elevators in the twin towers had stopped working. So rescuers started climbing up the stairs, but many were blocked by rubble or fire. Still, firefighters forged ahead, ignoring the danger.

The United States was under attack. About half an hour after the second tower was struck in New York City, hijackers crashed a third airplane. American Airlines Flight 77 hit the west side of the Pentagon, a five-sided concrete building that serves as headquarters for the U.S. Department of Defense, in Arlington, Virginia, just outside Washington, D.C. The plane’s fuel tanks exploded, and two giant fireballs blasted into the air.

American Airlines Flight 11 hit the north tower at 8:46 a.m. The impact of the crash tore a hole that stretched from the 93rd to 99th floors of the building. Smoke and flames poured out of the tower. Many people thought they had just seen a terrible accident. But 17 minutes later, a second plane flew into another one of the World Trade Center buildings—this time into the south tower.

The sound of an approaching airplane was too loud, and the plane seemed to be flying too low.

On September 11, 2001, people in New York City woke up to a beautiful late summer day. It was a Tuesday, and people were preparing for another day at work and school.