9/11 Terrorist Attack Explained

The September 11 attacks, commonly called 9/11, were coordinated terrorist attacks carried out against the United States on September 11, 2001.

19 attackers hijacked 4 commercial airplanes. 2 planes were flown into the World Trade Center in New York City, 1 was flown into the Pentagon in Virginia, and a 4th crashed in Pennsylvania after passengers and crew members attempted to regain control of the plane.

Who Was Involved in the 9/11 Attacks?

Al Qaeda

The attacks were carried out by 19 members of al Qaeda, an extremist organization led at the time by Osama bin Laden. Al Qaeda planned and organized the attacks over several years.

Al Qaeda was the organization responsible for planning and carrying out the September 11 attacks.

The organization was led at the time by Osama bin Laden. Khalid Sheikh Mohammed was a central planner of the operation.

The 19 hijackers were members of al Qaeda. Several received flight training in the United States before the attacks.

The United States

The attacks targeted locations in the United States that represented major parts of the country's economic, military, and political system. The U.S. government, military, law enforcement agencies, emergency workers, and local governments responded to the attacks and their aftermath.

Passengers and Flight Crews

Passengers and crew members were aboard all four hijacked airplanes.

First Responders

Firefighters, police officers, emergency medical workers, and other first responders entered damaged buildings and surrounding areas to rescue people and respond to the attacks. Hundreds of first responders died on September 11, and many others later developed illnesses connected to exposure to dust and hazardous materials at the attack sites.

The People

Thousands of people working in or visiting the World Trade Center, Pentagon, and surrounding areas were directly affected. The attacks also affected families, communities, travelers, businesses, and people throughout the United States and other countries.

The attacks killed 2,977 victims, not including the 19 hijackers. The victims included people aboard the four airplanes, people inside and around the World Trade Center and Pentagon, and emergency workers who responded to the attacks.

What Happened on 9/11?

4 commercial airplanes were hijacked on the morning of September 11, 2001.

American Airlines Flight 11

Flight 11 was traveling from Boston to Los Angeles. Hijackers took control of the airplane and flew it into the North Tower of the World Trade Center in New York City. 92 people were aboard the plane, including 11 crew members, 76 passengers, and 5 hijackers.

United Airlines Flight 175

Flight 175 was also traveling from Boston to Los Angeles. Hijackers flew it into the South Tower of the World Trade Center. 65 people were aboard the plane, including 9 crew members, 51 passengers, and 5 hijackers.

American Airlines Flight 77

Flight 77 was traveling from Washington Dulles International Airport to Los Angeles. Hijackers flew it into the Pentagon, the headquarters of the U.S. Department of Defense. 64 people were aboard the plane, including 6 crew members, 53 passengers, and 5 hijackers.

United Airlines Flight 93

Flight 93 was traveling from Newark, New Jersey, to San Francisco. After learning about the other attacks, passengers and crew members attempted to regain control of the airplane. The plane crashed near Shanksville, Pennsylvania. Investigators concluded that the hijackers intended to attack another location in Washington, D.C. 44 people were aboard the plane, including 7 crew members, 33 passengers, and 4 hijackers.

How Did the 9/11 Attacks Happen?

At the time, airport and airline security procedures were different from those used today. Airline passengers were generally able to move more freely through airport security, and cockpit security was less strict.

The attackers boarded commercial flights carrying passengers and took control of the airplanes after they were in the air. The hijackers then used the airplanes themselves as weapons.

During the attacks, some passengers and crew members used Airfones, along with some cell phone calls, to contact family members, airlines, and emergency services. These calls helped people on the ground learn what was happening aboard the planes and helped passengers on Flight 93 learn about the other attacks.

The attacks were planned in advance by al Qaeda members in several countries. After the attacks, investigations examined how the plot developed and how information available to U.S. government agencies before September 11 had been handled.

Where Did the 9/11 Attacks Take Place?

New York City

Two airplanes struck the World Trade Center in Lower Manhattan. Both the North Tower and South Tower later collapsed. Several nearby buildings were also damaged or destroyed.

Arlington, Virginia

American Airlines Flight 77 struck the Pentagon, located outside Washington, D.C. Part of the building was heavily damaged.

Shanksville, Pennsylvania

United Airlines Flight 93 crashed into a field near Shanksville after passengers and crew members attempted to regain control of the airplane.

Why Did Al Qaeda Carry Out the Attacks?

Al Qaeda's leaders described several political and religious reasons for targeting the United States. Al Qaeda's leaders publicly stated that their reasons for targeting the United States included:

1. The presence of U.S. military forces in Saudi Arabia
2. U.S. support for Israel
3. U.S. policies and military actions in the Middle East
4. Opposition to governments in the region that worked with the United States

Al Qaeda also presented its goals through its own religious and political beliefs. These stated reasons were part of the organization's explanation for carrying out the attacks. Its views did not represent Islam or Muslims as a whole. Muslim leaders and communities around the world condemned the attacks.

What Happened After 9/11?

The attacks caused major changes in U.S. foreign policy, national security, air travel, and government operations.

War in Afghanistan

The United States demanded that Afghanistan's Taliban government turn over Osama bin Laden and other al Qaeda leaders who were operating in the country.

After the Taliban refused U.S. demands, the United States and its allies began military operations in Afghanistan in October 2001. The war continued for nearly 20 years before U.S. forces withdrew in 2021.

Department of Homeland Security

The federal government created the Department of Homeland Security in 2002 to bring several government agencies together to help prevent and respond to threats against the United States.

Airport Security

Airport security became much stricter. The Transportation Security Administration, commonly called the TSA, was created in 2001 to oversee security at U.S. airports. Cockpit doors were strengthened, passenger screening increased, and new security rules were introduced.

USA PATRIOT Act

Congress passed the USA PATRIOT Act in October 2001. The law expanded some government powers used to investigate terrorism and gather information.

Intelligence and Security Changes

The federal government changed how intelligence agencies collected and shared information about possible threats. The attacks also led to major changes in emergency planning and national security policy.

1. Improving communication between police, firefighters, emergency medical workers, and government agencies
2. Creating plans for responding to large attacks and disasters
3. Increasing training for emergency workers
4. Improving evacuation plans for buildings and public spaces
5. Increasing security at airports, government buildings, transportation systems, and other important locations
6. Developing systems that allow different government agencies to coordinate during an emergency

When Did the 9/11 Attacks Happen?

The attacks took place on Tuesday, September 11, 2001.

8:46 a.m.

American Airlines Flight 11 struck the North Tower of the World Trade Center.

9:03 a.m.

United Airlines Flight 175 struck the South Tower.

9:37 a.m.

American Airlines Flight 77 struck the Pentagon.

9:59 a.m.

The South Tower collapsed.

10:03 a.m.

United Airlines Flight 93 crashed near Shanksville, Pennsylvania.

10:28 a.m.

The North Tower collapsed. Within less than two hours, the attacks had killed thousands of people and caused major changes to U.S. national security, foreign policy, and everyday air travel.