NEW YORK/WASHINGTON — The United States is marking the 25th anniversary of the September 11, 2001 terrorist attacks on Friday with solemn ceremonies in New York, at the Pentagon in Virginia and near Shanksville, Pennsylvania, remembering the 2,977 victims of the deadliest terrorist attack in American history and reflecting on a quarter-century that transformed U.S. security, foreign policy and everyday life.

Twenty-five years after four commercial airliners were hijacked by 19 al-Qaeda terrorists, relatives of the victims, survivors, first responders, national leaders and members of the public are gathering at the three attack sites. Bells will toll, names will be read aloud, flags will fly at half-staff and moments of silence will mark the precise times when the attacks unfolded.

For millions who lived through September 11, the images remain almost impossible to separate from personal memory: the clear blue morning sky, a burning tower in Lower Manhattan, the second aircraft striking the South Tower on live television, the Pentagon in flames, people fleeing through streets covered in dust, and the wreckage of United Airlines Flight 93 in rural Pennsylvania.

But the 25th anniversary carries another significance. An entire generation has now reached adulthood without any personal memory of 9/11. What was once a shared national trauma witnessed in real time is increasingly becoming history that must be taught, documented and explained to people born after the attacks. President Donald Trump emphasized that generational transition in his 2026 Patriot Day proclamation, saying that the promise to “Never Forget” must be passed to those who did not experience the attacks themselves.

The original contemporary account also describes 9/11 as an event that came to define a generation of American foreign, intelligence and security policy, noting that 2,977 victims died that day and that the attacks were followed nine days later by President George W. Bush’s declaration of a “War on Terror.”

At New York’s National September 11 Memorial & Museum, the official 25th-anniversary ceremony is scheduled to begin at 8:30 a.m. Families of victims will again read the names of those killed. The Memorial’s annual reading includes 2,983 names — the 2,977 people killed in the September 11 attacks and the six victims of the February 26, 1993 bombing of the World Trade Center.

This year, for the first time, the ceremony will include seven moments of silence rather than six. Six correspond to the key moments of September 11 itself: 8:46 a.m., when American Airlines Flight 11 struck the North Tower; 9:03 a.m., when United Airlines Flight 175 hit the South Tower; 9:37 a.m., when American Airlines Flight 77 struck the Pentagon; 9:59 a.m., when the South Tower collapsed; 10:03 a.m., when Flight 93 crashed near Shanksville; and 10:28 a.m., when the North Tower fell.

A seventh silence will follow the reading of the names to honor people who have died in the years since from illnesses associated with exposure to toxic dust, smoke and debris after the attacks. The 9/11 Memorial & Museum said the additional observance will become a permanent part of future anniversary ceremonies.

That change highlights one of the most painful aspects of 9/11’s continuing legacy: its death toll did not effectively end on September 11, 2001. Firefighters, police officers, emergency workers, construction workers, volunteers, Lower Manhattan residents and others were exposed to a complex mixture of airborne contaminants during rescue, recovery and cleanup operations.

The federal World Trade Center Health Program says thousands continue to suffer from physical and mental health conditions associated with 9/11 exposure. The program now serves nearly 150,000 members across all 50 states and U.S. territories, including responders and survivors. Researchers warn that health consequences could continue emerging for decades.

At the Pentagon in Arlington, Virginia, President Trump is scheduled to participate in the 25th-anniversary commemoration. He formally proclaimed September 11, 2026, Patriot Day and ordered U.S. flags on federal property to be flown at half-staff in honor of the victims. Congress established September 11 as Patriot Day in December 2001.

Vice President JD Vance is scheduled to attend the New York observance, while officials and families are gathering at other memorial sites around the country. Earlier this week, Trump participated in a remembrance event in Washington featuring a 21-foot steel beam recovered from the South Tower, part of a nationwide memorial tour organized by the Tunnel to Towers Foundation.

In Pennsylvania, remembrance will center on Flight 93 National Memorial, where the 40 passengers and crew members who died aboard United Airlines Flight 93 are honored.

The National Park Service has scheduled a morning observance from 8:30 to 10:30 a.m. near the Wall of Names. Family members will read the names of the passengers and crew, and the Bells of Remembrance will sound in their honor. A separate afternoon ceremony from 1:00 to 2:30 p.m. will include remarks, music and a public wreath-laying.

Flight 93 occupies a unique place in the history of September 11 because the people aboard learned through telephone calls that other hijacked planes had already been used as weapons. Passengers and crew members then attempted to retake control of their aircraft.

As they fought their way toward the cockpit, the hijackers deliberately crashed the Boeing 757 into a field near Shanksville at 10:03 a.m. All 33 passengers and seven crew members, as well as the four hijackers, died. Investigators concluded that the intended target was probably a major government building in Washington, most likely the U.S. Capitol. The 9/11 Commission said the passengers’ actions may have saved the Capitol or the White House and almost certainly saved additional lives.

The attacks had begun just 77 minutes earlier.

At 8:46 a.m., American Airlines Flight 11 crashed into floors 93 through 99 of the World Trade Center’s North Tower.

At 9:03 a.m., United Airlines Flight 175 struck floors 77 through 85 of the South Tower, instantly eliminating any doubt that the United States was under coordinated attack.

At 9:37 a.m., American Airlines Flight 77 slammed into the Pentagon.

Twenty-two minutes later, at 9:59 a.m., the South Tower collapsed. Flight 93 crashed at 10:03 a.m. The North Tower fell at 10:28 a.m. By the end of the morning, the World Trade Center complex had been devastated, part of the Pentagon was destroyed, and the United States had entered a new era.

The 2,977 victims came from more than 90 countries and represented an extraordinary range of backgrounds, professions, religions and nationalities. The dead included office workers, restaurant employees, airline passengers and crews, firefighters, police officers, military personnel, government workers and visitors. The National September 11 Memorial & Museum describes the victims as ranging in age from two-and-a-half to 85.

Beyond the United States, commemorations are also taking place. In London, the charity SINCE 9/11 is holding a 25th-anniversary event at Queen Elizabeth Olympic Park near the 9/11 memorial sculpture created by artist Miya Ando. The sculpture incorporates steel recovered from the World Trade Center and has become the focal point for British remembrance of the attacks.

Yet the anniversary is not only about what happened that morning. It is also a moment to examine what followed.

Within days of the attacks, the United States had embarked on a fundamental transformation of its national security system. President George W. Bush declared a global “War on Terror.” U.S. forces invaded Afghanistan in October 2001 after the Taliban refused American demands regarding Osama bin Laden and al-Qaeda. Two years later, the United States led the invasion of Iraq — a war whose connection to the broader post-9/11 security environment would become one of the most controversial elements of that era.

At home, airport security was overhauled. The Transportation Security Administration was created in November 2001, and responsibility for screening airline passengers was federalized. Cockpit doors were strengthened, passenger screening expanded and aviation security procedures that would once have seemed extraordinary became routine.

The Department of Homeland Security was established, bringing together numerous agencies under a new structure intended to prevent terrorism and protect the country. The intelligence community was reorganized, counterterrorism operations expanded, terrorist watchlists grew, and the office of the Director of National Intelligence and the National Counterterrorism Center were created.

Those reforms followed a devastating assessment of the failures preceding the attacks.

The bipartisan 9/11 Commission, established by Congress, concluded after one of the most extensive investigations in U.S. history that the government had suffered failures in four broad areas: “imagination, policy, capabilities, and management.” Investigators found that agencies possessed fragments of relevant information but failed to understand the scale and nature of the threat or connect key pieces of intelligence in time to stop the plot.

The commission also identified missed opportunities involving terrorist watchlists, visa information, aviation security and the handling of intelligence about suspected extremists. Its findings helped drive some of the largest changes to the U.S. intelligence system since the creation of the CIA after World War II.

But the post-9/11 response also produced a controversial legacy. The wars in Afghanistan and Iraq cost enormous numbers of lives and trillions of dollars. The United States expanded electronic surveillance and counterterrorism powers. The detention facility at Guantánamo Bay, CIA interrogation practices, rendition programs and abuses of prisoners generated intense legal and human-rights criticism.

Muslim Americans and people perceived to be Middle Eastern, Arab or South Asian also faced heightened suspicion, discrimination and, in some cases, violence in the years after the attacks. A quarter-century later, historians and policymakers continue to debate where necessary security measures ended and excessive government power began.

Al-Qaeda itself was severely weakened by years of U.S. and allied military and intelligence operations. Osama bin Laden was killed by U.S. Navy SEALs in Pakistan in May 2011, nearly ten years after the attacks. But the organization did not disappear. It evolved into a more decentralized network of regional affiliates, some of which remain active in Africa, the Middle East and South Asia. Reuters reported ahead of the anniversary that al-Qaeda today is far weaker than the organization that carried out 9/11 but continues to exert influence through affiliates and allied militant organizations.

The threat environment has also become far more complex. Counterterrorism remains a major responsibility for intelligence agencies, but governments now simultaneously confront cyberattacks, state-backed sabotage, disinformation, drone warfare and strategic competition involving countries such as Russia, China and Iran. On the anniversary, Britain’s MI5 director warned that intelligence agencies cannot simply prepare to prevent another version of the last attack; the next major security shock could emerge from a threat that governments are currently overlooking.

Perhaps the most profound change at the 25-year mark, however, is generational.

People born on September 11, 2001 are now 25 years old. University students, young professionals and even some members of the military know the attacks only through family stories, classroom lessons, television footage, photographs and the political world they inherited. Reuters reported this week that for younger adults, 9/11 is increasingly understood as history rather than memory, even though the security systems, wars and political debates that followed it shaped much of their lives.

That is why this anniversary carries unusual weight.

The central challenge of September 11, 2026, is no longer simply whether Americans remember where they were when the planes struck. It is whether a country now separated from that morning by a quarter-century can preserve the stories of the people who died, understand the failures that allowed the attacks to happen, honor the responders still suffering from their consequences, and critically examine the decisions made in the name of preventing another attack.

On Friday morning, those complicated questions will temporarily give way to something much simpler.

At Ground Zero, relatives will again speak the names of mothers and fathers, husbands and wives, sons and daughters, friends and colleagues. At the Pentagon, families will gather beside the memorial benches. In Pennsylvania, bells will sound for the passengers and crew who fought back aboard Flight 93. Across the country, American flags will hang at half-staff.

And 25 years after a clear September morning changed the United States and much of the world, the promise first made amid the ruins will be repeated once more:

Never Forget.