Today, 11 September 2026, marks 25 years since the terrorist attacks of 11 September 2001. The attacks defined the opening of the 21st century in the United States and changed foreign policy, domestic security and everyday life, with effects that reached far beyond New York, Washington and Pennsylvania.

That morning, 19 members of al-Qaeda hijacked four commercial aircraft. American Airlines Flight 11, which had left Boston for Los Angeles, struck the North Tower of the World Trade Center at 8:46 a.m. local time. At 9:03 a.m., United Airlines Flight 175 struck the South Tower. The second impact, shown live, made it clear that this was a coordinated attack. A third aircraft, American Airlines Flight 77, struck the Pentagon, headquarters of the Department of Defense, at 9:37 a.m. The fourth, United Airlines Flight 93, crashed at 10:03 a.m. into a field near Shanksville, Pennsylvania, after passengers and crew, learning by phone about New York, tried to regain control. No one aboard survived. Later investigations indicated that the likely target was a major building in Washington.

The South Tower collapsed at 9:59 a.m., less than an hour after it was struck. The North Tower collapsed at 10:28 a.m. Firefighters, police officers, paramedics and other rescuers went into the buildings as thousands of people fled; many of them were killed when the towers fell. The attacks killed nearly 3,000 people, not counting the 19 hijackers. The victims came from the United States and many other countries. Hundreds of emergency workers were among the dead. In later years, many of those involved in recovery at Ground Zero developed serious illnesses linked to dust and other substances released after the collapse.

The attacks were organised by al-Qaeda, then led by Osama bin Laden. The United States and its partners launched an international campaign against the network. On 7 October 2001 they began military operations in Afghanistan against the Taliban regime and al-Qaeda; the war would last almost two decades. Bin Laden was located and killed by U.S. forces in Pakistan in May 2011.

On 12 September 2001, NATO invoked Article 5 of the Washington Treaty for the first time in its history: an attack against one ally is considered an attack against all. Inside the United States, the Transportation Security Administration was created in November 2001 and changed airport screening. The Department of Homeland Security was established in 2002. Surveillance powers were expanded; some of those measures later prompted debate about the balance between security, privacy and civil liberties.

The site of the Twin Towers became known as Ground Zero. The complex was rebuilt; One World Trade Center is now among the landmarks of the area. The National September 11 Memorial & Museum includes two pools in the footprints of the former towers, with the names of those killed on 11 September 2001 and in the 1993 World Trade Center bombing inscribed around them. In Pennsylvania, the Flight 93 National Memorial, run by the National Park Service, commemorates the passengers and crew. There is also a memorial at the Pentagon.

In New York, the 25th-anniversary ceremony at Memorial Plaza includes the reading of names by victims’ families and moments of silence tied to the times of the attacks. In 2026 the programme provides for seven moments of silence: six for the striking and collapse of the towers, the Pentagon and Flight 93, and a seventh, now part of the ceremony, for those who later died of 9/11-related illness. Ceremonies are also being held at the Pentagon and at the Pennsylvania memorial. For families, survivors and rescuers, the anniversary is not only a date on the calendar. It is the memory of a morning that permanently changed thousands of lives. For those born after 2001, 11 September already belongs to history; its consequences remain visible in aviation security, counterterrorism policy and international relations.

Photo: Carol M. Highsmith / Library of Congress, public domain. The Twin Towers of the World Trade Center in New York, photographed before 11 September 2001. Archive photograph, not from the 2026 ceremony. The image was cropped to 16:9.

Sources consulted: 25th Anniversary Commemoration | National September 11 Memorial & Museum; Statement by the North Atlantic Council, 12 September 2001 | NATO; Flight 93 National Memorial | National Park Service.