At 8:45 a.m. on a clear Tuesday morning, an American Airlines Boeing 767 loaded with 20,000 gallons of jet fuel crashes 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 at about 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 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 U.S. in the months before September 11 and acted as the "muscle" in the operation. The 19 attackers 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 the ordinary commuter jets into guided missiles.

As millions watched in horror the events unfolding in New York, American Airlines Flight 77 circled over downtown Washington and slammed into the west side of the Pentagon military headquarters at 9:45 a.m. Jet fuel from the Boeing 757 caused a devastating inferno that led to a structural collapse of a portion of the giant concrete building. All told, 125 military personnel and civilians were killed in the Pentagon along with all 64 people aboard the airliner.

Less than 15 minutes after the terrorists struck the nerve center of the U.S. military, the horror in New York took a catastrophic turn for the worse when the south tower of the World Trade Center collapsed in a massive cloud of dust and smoke. The structural steel of the skyscraper, built to withstand winds in excess of 200 mph and a large conventional fire, could not withstand the tremendous heat generated by the burning jet fuel. At 10:30 a.m., the other Trade Center tower collapsed. Close to 4,000 people died in the World Trade Center and its vicinity, including a staggering 343 firefighters and 23 policemen who were struggling to complete an evacuation of the buildings and save the office workers trapped on higher floors. Only six people in the World Trade Center towers at the time of their collapse survived. Almost 10,000 other people were treated for injuries, many severe.

Meanwhile, a fourth California-bound plane--United Flight 93--was hijacked about 40 minutes after leaving Newark International Airport in New Jersey. Because the plane had been delayed in taking off, passengers on board learned of events in New York and Washington via cell phone and Airfone calls to the ground. Knowing that the aircraft was not returning to an airport as the hijackers claimed, a group of passengers and flight attendants planned an insurrection. One of the passengers, Thomas Burnett, Jr., told his wife over the phone that "I know we're all going to die. There's three of us who are going to do something about it. I love you, honey." Another passenger--Todd Beamer--was heard saying "Are you guys ready? Let's roll" over an open line. Sandy Bradshaw, a flight attendant, called her husband and explained that she had slipped into a galley and was filling pitchers with boiling water. Her last words to him were "Everyone's running to first class. I've got to go. Bye."

The passengers fought the four hijackers and are suspected to have attacked the cockpit with a fire extinguisher. The plane then flipped over and sped toward the ground at upwards of 500 miles per hour, crashing in a rural field in western Pennsylvania at 10:10 a.m. All 45 people aboard were killed. Its intended target is not known, but theories include the White House, the U.S. Capitol, the Camp David presidential retreat in Maryland, or one of several nuclear power plants along the eastern seaboard.

At 7 p.m., President George W. Bush, who had spent the day being shuttled around the country because of security concerns, returned to the White House. At 9 p.m., he delivered a televised address from the Oval Office, declaring "Terrorist attacks can shake the foundations of our biggest buildings, but they cannot touch the foundation of America. These acts shatter steel, but they cannot dent the steel of American resolve." In a reference to the eventual U.S. military response he declared: "We will make no distinction between the terrorists who committed these acts and those who harbor them."

Operation Enduring Freedom, the U.S.-led international effort to oust the Taliban regime in Afghanistan and destroy Osama bin Laden's terrorist network based there, began on October 7.