On September 11, 2001, at 8:45 a.m. on a clear Tuesday morning, an American Airlines Boeing 767 loaded with 20,000 gallons of jet fuel crashed into the north tower of the World Trade Center in New York City. The impact left a gaping, burning hole near the 80th floor of the 110-story skyscraper, instantly killing hundreds of people and trapping hundreds more in higher floors. As the evacuation of the tower and its twin got underway, television cameras broadcasted live images of what initially appeared to be a freak accident. Then, 18 minutes after the first plane hit, a second Boeing 767–United Airlines Flight 175–appeared out of the sky, turned sharply toward the World Trade Center and sliced into the south tower near the 60th floor. The collision caused a massive explosion that showered burning debris over surrounding buildings and the streets below. America was under attack.
The attackers were Islamic terrorists from Saudi Arabia and several other Arab nations. Reportedly financed by Saudi fugitive Osama bin Laden's al-Qaeda terrorist organization, they were allegedly acting in retaliation for America's support of Israel, its involvement in the Persian Gulf War and its continued military presence in the Middle East. Some of the terrorists had lived in the United States for more than a year and had taken flying lessons at American commercial flight schools. Others had slipped into the country in the months before September 11 and acted as the "muscle" in the operation. The 19 terrorists easily smuggled box-cutters and knives through security at three East Coast airports and boarded four flights bound for California, chosen because the planes were loaded with fuel for the long transcontinental journey. Soon after takeoff, the terrorists commandeered the four planes and took the controls, transforming ordinary commuter jets into guided missiles.

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