From flight training and entry into the US to the coordinated attacks on New York and Washington, here is how the September 11, 2001, plot unfolded and transformed global security
New York: September 11, 2001, began like any other morning in the United States. People headed to work, planes took off and thousands of employees started their day inside New York’s World Trade Center.
Within hours, 19 Al-Qaeda-linked terrorists would carry out an attack that would reshape American security, foreign policy and the global fight against terrorism.
At 8:46 am, American Airlines Flight 11 crashed into the World Trade Center’s North Tower. Seventeen minutes later, United Airlines Flight 175 struck the South Tower, making the coordinated nature of the attack clear.
A third hijacked aircraft hit the Pentagon near Washington, DC. A fourth, United Airlines Flight 93, crashed into a field near Shanksville, Pennsylvania, after passengers fought the hijackers.
The attacks killed 2,977 people. Twenty-five years later, 9/11 remains a defining moment in US history and continues to influence global politics, aviation security and counterterrorism.
What happened on September 11, 2001?
Nineteen Al-Qaeda-linked terrorists hijacked four commercial passenger aircraft.
The hijackers flew two planes into the World Trade Center’s Twin Towers in New York. They flew a third aircraft into the Pentagon, the US Department of Defense headquarters near Washington.
The fourth aircraft, Flight 93, headed towards Washington. Passengers and crew members learned about the other attacks through phone calls and decided to fight back.
They tried to reach the cockpit and regain control of the aircraft. They could not take control, but their resistance stopped the hijackers from reaching their intended target. Flight 93 crashed into a field near Shanksville.
Everyone aboard the four aircraft died, while thousands of people on the ground also lost their lives.
The World Trade Center attacks
American Airlines Flight 11 left Boston’s Logan International Airport at 7:59 am for Los Angeles. At 8:46 am, the hijackers crashed it into the North Tower.
United Airlines Flight 175 left Boston at 8:14 am, also heading to Los Angeles. At 9:03 am, the hijackers crashed it into the South Tower.
The second impact immediately showed the world that the United States faced a coordinated terrorist attack.
Smoke filled the New York skyline as television networks broadcast live images of the burning towers. People rushed out of the buildings while firefighters, police officers and other emergency workers entered the disaster zone to rescue those trapped inside.
The South Tower collapsed at 9:59 am. The North Tower followed at 10:28 am.
The collapsing towers turned the World Trade Center complex and surrounding streets into a massive field of debris.
The Pentagon attack
As New York battled the attacks, another hijacked aircraft headed towards Washington.
American Airlines Flight 77 left Dulles International Airport at 8:20 am for Los Angeles. The hijackers took control of the plane and turned it towards the Pentagon.
At around 9:37 am, the aircraft crashed into the building, killing everyone aboard and people inside the Pentagon.
The attack showed that the terrorists had targeted more than New York’s financial centre. They had also targeted a major symbol of American military power and national security.
Flight 93 and the passengers who fought back
United Airlines Flight 93 left Newark Airport at 8:41 am for San Francisco.
After the hijacking, passengers learned through telephone calls that other planes had already struck targets in New York and Washington.
Several passengers and crew members decided to resist. They tried to reach the cockpit and take control of the aircraft.
Their attempt failed, but Flight 93 never reached its intended target. The plane crashed near Shanksville, Pennsylvania.
The passengers’ resistance has since become one of the most powerful stories of courage and sacrifice from the September 11 attacks.
2,977 people died in the attacks
The September 11 attacks killed 2,977 people, including passengers and crew members, civilians at the World Trade Center and Pentagon, and emergency responders.
New York suffered the largest loss of life.
The emergency response also came at a devastating cost. The New York City Fire Department lost 343 members. The New York Police Department lost 23 officers, while the Port Authority Police Department lost 37 officers.
The human toll continued long after September 11, 2001. Many first responders and other people who faced toxic conditions at Ground Zero later developed serious illnesses and died in the following years.
The impact of 9/11 therefore extended far beyond the day of the attacks.
Who carried out the attacks?
Al-Qaeda carried out the attacks under the leadership of Osama bin Laden.
The organisation had already targeted American interests. The 1998 US embassy bombings in Kenya and Tanzania and the 2000 attack on the USS Cole had established bin Laden as a major terrorist threat to the United States.
After 9/11, the US made the hunt for bin Laden and the dismantling of Al-Qaeda central to its counterterrorism campaign.
Nearly a decade later, on May 2, 2011, US special forces killed bin Laden during a raid in Abbottabad, Pakistan.
How did the hijackers prepare?
Al-Qaeda developed the 9/11 plot over several years and divided the 19 hijackers into four teams, with each team assigned to one aircraft.
Four hijackers received flight training: Mohamed Atta, Marwan al-Shehhi, Hani Hanjour and Ziad Jarrah. They eventually took control of the four aircraft and flew them during the attacks.
Investigators identified Mohamed Atta as the plot’s central operational planner.
Several hijackers also trained at US flight schools. They learned to fly small aircraft and developed basic cockpit skills.
Investigators later found that authorities had received information about some suspicious activities but had failed to share important details effectively across agencies.
How did the hijackers enter the US?
The 9/11 Commission found that most of the 19 hijackers entered the United States with valid passports and US visas.
They arrived at different times and often passed through routine immigration checks like other travellers.
Investigators later uncovered irregularities in their travel and immigration records. Some provided false or misleading information on visa applications, while others violated visa or immigration rules after entering the country.
The investigation also exposed major weaknesses in information sharing between US intelligence and security agencies.
Different agencies held pieces of information about suspicious activities, but officials did not always share those details with the right agencies in time.
The findings prompted major changes to visa checks, immigration screening and information-sharing systems.
How 9/11 changed America
The attacks transformed US security and foreign policy.
President George W. Bush’s administration launched a global campaign against terrorism. On October 7, 2001, the United States began military operations in Afghanistan, targeting Al-Qaeda and the Taliban government that had provided shelter to bin Laden and his organisation.
The US also tightened domestic security. Airports introduced stricter screening, while government agencies increased cooperation on counterterrorism and national security.
The government later created the Department of Homeland Security and carried out a major restructuring of the country’s intelligence and security systems.
9/11 transformed airport security
Many airport security measures that passengers consider routine today became much stricter after 9/11.
Security agencies changed their approach to aircraft hijackings. Before the attacks, authorities largely prepared for traditional hijackings involving negotiations and hostage situations.
9/11 demonstrated a far more dangerous possibility: terrorists could turn a passenger aircraft itself into a weapon.
The 9/11 Commission found that the hijacking protocols in place before the attacks had not adequately prepared authorities for such a scenario.
The attacks therefore reshaped aviation security in the United States and around the world.
The ‘War on Terror’ changed global politics
After 9/11, terrorism became a central issue in international politics and military strategy.
The US launched operations against Al-Qaeda and pursued networks that supported terrorist organisations. The war in Afghanistan continued for years and became one of America’s longest military campaigns.
The shift in US foreign policy also affected the Middle East and South Asia. Countries around the world strengthened security policies, expanded intelligence cooperation and reassessed their approach to terrorist threats.
Ground Zero became a place of remembrance
The site where the World Trade Center towers once stood now houses the 9/11 Memorial & Museum, which honours the victims of the attacks.
Every September 11, victims’ families gather there and read the names of those who died.
On the 25th anniversary, the memorial held a special remembrance ceremony. The programme began at 8:30 am, with the first moment of silence at 8:46 am, marking the time Flight 11 struck the North Tower.
The ceremony included seven moments of silence to remember key moments of the attacks, including the strikes on the Twin Towers, their collapse, the Pentagon attack and the crash of Flight 93.
Twenty-five years later, 9/11 continues to shape how the world understands terrorism, national security and the consequences of an attack that changed history.
