25 years of the September 11 tragedy: what happened and what changed in the world

On September 11, 2001, the United States suffered the largest terrorist attack in its history. That day, 19 al-Qaeda militants hijacked four passenger planes and used them as weapons. Two airliners crashed into the World Trade Center towers in New York, a third struck the Pentagon near Washington, and the fourth went down in Pennsylvania. A total of 2,977 people were killed. 

Even 25 years later, September 11 remains an event that changed approaches to international security, aviation, counterterrorism, and foreign policy. 

UNN recalls how it all unfolded that day. 

Timeline of the events of September 11, 2001

The morning of September 11 was clear and warm. Four planes departed from airports in the northeastern United States for California. They were American Airlines Flights 11 and 77, as well as United Airlines Flights 175 and 93.

At 8:46 a.m. local time, American Airlines Flight 11 crashed into the North Tower of the World Trade Center. At first, many people still did not understand what had happened and could not even imagine that it was a terrorist attack. But just 17 minutes later, at 9:03 a.m., United Airlines Flight 175 struck the South Tower. It then became clear that this was not a tragic accident and that the United States had suffered a large-scale terrorist attack. 

At 9:37 a.m., American Airlines Flight 77 crashed into the western side of the Pentagon. At 9:59 a.m., the South Tower of the World Trade Center collapsed, and at 10:03 a.m., United Airlines Flight 93 went down near Shanksville, Pennsylvania. After learning by phone about the earlier attacks, passengers and crew members attempted to wrest control of the plane from the terrorists. According to the findings of the 9/11 Commission, the plane was likely heading for the Capitol or the White House. 

At 10:28 a.m., the North Tower collapsed. From the first impact to the fall of the last tower, 102 minutes passed. The United States closed its airspace, while thousands of firefighters, police officers, medical workers, and rescuers headed to the attack sites. For the FBI, the crash sites and the destruction of the World Trade Center became the largest crime scenes in the bureau’s history. 

How many people died and how the world endured the tragedy

The September 11, 2001 attacks claimed the lives of 2,977 people (not counting the 19 suicide terrorists). The victims included residents and citizens of more than 90 countries. More than 2,600 people died at the World Trade Center site, 125 at the Pentagon, and another 246 people became victims of the hijackings of the four planes. Forty passengers and crew members who resisted the attackers died aboard Flight 93. 

The consequences for people who worked at the attack sites or lived nearby became a tragedy in their own right. Dust and toxic substances released after the towers collapsed caused numerous illnesses among rescuers, emergency responders, and Lower Manhattan residents. 

The World Trade Center Health Program continues to provide medical assistance to those affected even a quarter of a century later. As of 2024, it had more than 132,000 participants, some of whom have already died, including from illnesses included on the program’s list of certified conditions. 

The first days after the attacks were marked by shock, mourning, and unprecedented attention from the world’s media. In many countries, people took part in solidarity rallies with the United States, while Washington’s allies declared their readiness to fight terrorism together. NATO invoked Article 5 of the North Atlantic Treaty on collective defense for the first time in its history.

The attacks also had a significant economic impact. U.S. stock markets were closed for several days, air travel effectively came to a halt, and the global aviation industry entered a new era of security.

How the attacks changed global politics and security

The most important consequence of September 11 was the so-called "war on terror." On October 7, 2001, the United States and its allies launched a military operation in Afghanistan against the Taliban, which had provided shelter to al-Qaeda. Two years later, the United States began the war in Iraq, which became one of the White House’s most controversial decisions after the events of September 11. 

In addition, sweeping changes took place within the United States. After the attacks, Congress passed the USA PATRIOT Act, which significantly expanded the government’s powers in investigating terrorism, conducting surveillance, and accessing information. And in 2002, the U.S. Department of Homeland Security was established, bringing together 22 federal departments and agencies. 

Aviation security also changed fundamentally. The U.S. Transportation Security Administration was established; screening of passengers and baggage was tightened; access to areas near boarding gates was restricted; and cockpit doors were reinforced. New rules concerning carry-on luggage, liquids, screening, and other procedures were subsequently added. What had seemed extraordinary before 2001 gradually became a routine part of air travel. 

At the same time, the role of intelligence and data sharing among government institutions grew. After September 11, the United States restructured its counterterrorism system, strengthening coordination among intelligence agencies, police, and other authorities. The commission investigating the attacks specifically highlighted problems with information sharing among agencies and recommended creating a more integrated counterterrorism system. 

As a result, an intense debate emerged in society  over the boundary between security and civil liberties. Increased surveillance, expanded powers for intelligence agencies and law enforcement, as well as the practice of handling confidential information, became the subject of prolonged political and legal disputes. The 9/11 Commission itself warned that increased government control must be accompanied by the protection of privacy and civil rights. 

Twenty-five years later, it became clear that the legacy of September 11 extends far beyond changes to security systems. The terrorist threat became one of the key factors in international politics, while the wars launched after the attacks affected the Middle East, Central Asia, and the global security system for decades.

How the victims are being remembered 25 years later

In 2026, the United States is marking the 25th anniversary of the tragedy. The central commemorative events are taking place in New York, near the Pentagon, and at the Flight 93 memorial in Pennsylvania. On September 11, U.S. President Donald Trump is taking part in events honoring the victims, while the White House has declared the day Patriot Day and called for national flags to be flown at half-staff in honor of the 2,977 people who died. 

At the National September 11 Memorial in Lower Manhattan, relatives of the victims traditionally read out the names of those who died. This year, the ceremony has special significance: in addition to the six minutes of silence corresponding to key moments of the attacks, a seventh minute has been scheduled for the first time to honor people who died from illnesses linked to the consequences of the September 11 attacks. The ceremony  is private for the families of the victims, but it will be streamed online.

In the evening, New York’s sky will once again be illuminated by two powerful beams, Tribute in Light, at the site of the former twin towers. The installation first appeared six months after the attacks and has since become one of the main annual symbols commemorating the victims. In 2026, it will be supplemented for the first time by a special television broadcast dedicated to the 25th anniversary. 

Reminder

On Friday, September 11, 2,977 drones recreated the Twin Towers in New York in memory of the victims of the terrorist attack that took place 25 years ago.