Timeline of the September 11 Attacks

In 1979, the government of Afghanistan requests military intervention from the Soviet Union, in hopes of quelling Afghani rebels. At about the same time, Osama bin Laden, a member of a wealthy family from Saudi Arabia, leaves college to help Afghani rebels fight the invading Soviet Union. The rebels succeed in driving out the Soviets, and bin Laden returns to Saudi Arabia, energized by the victory. In 1988 or 1989, he forms a group called al-Qaida (in Arabic, "The Foundation") dedicated to driving Western influences and military forces out of the Middle East and to opposing the United States' support of Israel.

Bin Laden sets about creating strategies to achieve his goals, including tactics such as violence against civilians and suicide bombings. In 1993, al-Qaida-sponsored attacks kill 18 American soldiers in Somalia; in the same year, his group aids in a car bomb attack on the World Trade Center. The organization also claims responsibility for killing hundreds of other people in the U.S. embassies in Kenya and Tanzania in 1998.

In 1996, the war-torn country of Afghanistan is undergoing a new round of tumult. The Taliban, an extremist group bent on imposing a brutal brand of fundamental Islamic rule, takes control of the government and initiates sweeping changes. The political leanings of the Taliban are a good match for bin Laden's violent ideologies. He takes advantage of the Taliban's receptiveness and sets up a base of operations, including terrorist training centers, in Afghanistan. Both al-Qaida and the Taliban jointly profit from the opium trade to fund their military and political missions. Al-Qaida grows larger, gaining momentum and attracting more followers.

In 1996, Khalid Sheikh Mohammed, a Kuwait-born Islamic extremist and influential member of al-Qaida, pitches an idea for an attack on America to bin Laden. He proposes hijacking 10 commercial airplanes and guiding them into targets around the country. Bin Laden likes the idea. In 1998 or 1999, he gives Mohammed the go-ahead to begin planning and provides strategies, as well as funding, for Mohammed's tactical and operational expertise. He also scales back Mohammed's aspirations by limiting the attack to just four planes, believing that 10 would make the plan overly complicated and more likely to fail. Al-Qaida leaders begin screening recruits for their readiness to infiltrate the United States. They carefully select men who could potentially fly -- or train to fly -- commercial aircraft.

Bin Laden helps choose the lead hijacker, an Egyptian named Mohamed Atta. In 2000, Atta travels to the United States. Like the 18 other terrorists, he begins assimilating into society, attempting to avoid drawing undue attention to himself. Like a few of the other terrorists, Atta begins taking flying lessons, including a stint at an accelerated training program located in Florida. In 2001, the rest of the hijackers begin arriving in America. These secondary terrorists aren't slated to fly the hijacked planes. Instead, they plan to back up the primary pilot-hijackers and help them achieve their ultimate goals. The terrorists live scattered around the country, waiting for the cue to begin their operation.

On Sept. 11, 2001, Mohamed Atta and four other hijackers arrive at Portland (Maine) International Airport before 6 a.m. From there, they take a small plane to Boston's Logan International Airport. Then they board American Airlines Flight 11. Flight 11 takes off from Boston at 8 a.m., bound for Los Angeles. Meanwhile, the 17 other terrorists are busy boarding their own flights. Five hijackers board United Airlines Flight 175 in Boston, which takes off for Los Angeles at 8:14 a.m. Six minutes later, American Airlines Flight 77 leaves Washington Dulles International Airport, in Dulles, Va., with five terrorists aboard.

At 8:19 a.m., two attendants on Flight 11 tell ground personnel that the plane had been hijacked. They relay key information, such as the hijackers' seat numbers, that helps authorities begin their investigation immediately as the morning's events unfold. Within 20 minutes, the Federal Aviation Administration (FAA) has notified the North American Aerospace Defense Command (NORAD) about the suspected hijacking. At about the same time, the fourth and final plane, United Airlines Flight 93, departs Newark International Airport, in Newark, N.J., and heads toward San Francisco. Four hijackers prepare to make their moves.

As Flight 11 speeds toward New York City, air traffic controllers try to piece together what's happening in the skies. They overhear a man in the cockpit announcing to the passengers, "We have some planes. Just stay quiet and you will be OK." Not only does the statement confirm that the plane's been hijacked, but the man's use of the word planes, in the plural, also seems a harbinger of things to come. More planes will be -- or already have been -- hijacked.

At 8:45 a.m., Atta and his team deliberately crash Flight 11 into the North Tower of the World Trade Center in New York City. At 9:03, Flight 175 smashes into the South Tower.

Within five minutes, the FAA halts all takeoffs scheduled to fly to New York City or through New York City airspace. By 9:17 a.m., all New York City airports are shut down.

At 9:26 a.m., the FAA stops takeoffs for all civilian aircraft throughout the country. Five minutes later, President George W. Bush calls the plane incidents an "apparent terrorist attack on our country."

At 9:43 a.m. Flight 77 crashes into the Pentagon, in Virginia. Two minutes later, the White House is evacuated.

At 9:45, the FAA commands all aircraft already in the skies to land as soon as possible. That means air traffic controllers must somehow coordinate the unscheduled, and unprecedented, landing of nearly 4,500 planes.

At 10:05 a.m., the enormity of the attacks becomes much clearer as the South Tower of the World Trade Center collapses. Five minutes later, part of the Pentagon caves in as well.

At the same time, passengers aboard Flight 93, having learned of the other attacks via cell phones, attempt to wrest control of the plane from the hijackers, who crash the plane into a field in Pennsylvania. It's the only plane to have missed its target, which was presumably the U.S. Capitol.

At 10:28 a.m., with the now fully alert world watching on television, the North Tower of the World Trade Center comes crashing down. Now-iconic video footage and still photos capture many events of the day, from the planes hitting the towers to the billowing aftermath of their collapse into the streets of the city.

Although it's not even noon yet, all 19 hijackers are already dead, along with thousands of American victims, and a new era in history has begun.

At 8:30 p.m. on the evening of September 11, President Bush addresses the people of the United States and asserts that the country will win the war on terrorism.

Immediately after the attacks, United States intelligence agencies and political leaders begin preparations for a counterattack. Less than a month later, America invades Afghanistan, attacking Taliban and al-Qaida targets throughout the country. The Taliban is driven out of power, and al-Qaida groups are destroyed and scattered. The United States finds another enemy in Saddam Hussein, the leader of Iraq, who supposedly has links to al-Qaida. Although Hussein had limited contact with bin Laden's group and nothing to do with the September 11 attacks, America invades Iraq and removes Hussein from power. The United States Armed Forces continue to occupy both Iraq and Afghanistan.

In October 2004, a video of bin Laden airs on Arabic television. In the taped message, al-Qaida's leader, who had for years denied his involvement in the September 11 attacks, finally confesses that he played a lead role in the plot. The United States continues to offer a $25 million bounty to anyone who helps them catch or kill bin Laden. In spite of the unprecedented reward, al-Qaida's leader continues to evade detection for years.

On May 2, 2011, the United States military conducts a secret operation at a compound located in Abbottabad, Pakistan, not far from a Pakistani military base. Teams made up of 12 Navy SEALs flying in two helicopters enter the home and find bin Laden, along with several other people, including some of bin Laden's relatives. The SEALs shoot and kill bin Laden and bury his body at an undisclosed location in the North Arabian Sea. With bin Laden dead, the hunt for the world's most wanted man is over, but the violence and conflict he helped spark continue.