9/11 at 25: What happened that morning and how it changed the world

Close to a third of the US population was born after 2001, meaning millions now learn about that day only through history lessons, memorials and the accounts of survivors and family members. As the nation marks 25 years since the attacks with ceremonies and tributes across the country, here is a longer look back at what happened, who carried it out, how many people died, and why the day continues to shape American life today.

What exactly happened that morning?

The attacks unfolded over roughly 100 minutes on what began as a clear, ordinary Tuesday. At 8:46am, hijackers crashed American Airlines Flight 11 into the North Tower of the World Trade Center in New York, tearing a hole through the building’s upper floors. Seventeen minutes later, at 9:03am, United Airlines Flight 175 struck the South Tower, an impact seen live on television by millions who had already tuned in to cover the first crash, turning a suspected accident into a confirmed attack in real time.

At 9:37am, a third hijacked plane, American Airlines Flight 77, slammed into the Pentagon just outside Washington, DC. The South Tower collapsed at 9:59am, followed by the North Tower at 10:28am, reducing both structures to rubble within under two hours of the first impact.

A fourth aircraft, United Airlines Flight 93, had also been hijacked and was believed to be headed toward a target in Washington, DC. Passengers and crew, who had learned of the earlier attacks through phone calls to loved ones, fought back against the hijackers. The plane crashed into a field near Shanksville, Pennsylvania, at 10:03am, killing everyone on board but preventing the aircraft from reaching its intended target, according to USA Today. Rescue workers spent weeks afterwards searching through the rubble in New York for survivors and remains.

How did the hijackers enter the country?

The 19 hijackers spent months preparing for the coordinated attack, with some entering the United States as early as 2000, USA Today reports. Most entered on legally issued tourist or business visas, and several took flight lessons at US flight schools in the months before the attacks in order to learn how to pilot, though not land, commercial aircraft.

The group operated in small cells, with members living in states including Florida, California and Virginia while they trained and prepared, before converging to board the four flights on the morning of 11 September.

Who planned the 9/11 attacks?

The attacks were planned and carried out by al-Qaida, the terrorist network led by Osama bin Laden. US federal investigators say the plot was put together by Khalid Sheikh Mohammed, with bin Laden and his deputy, Ayman al-Zawahri, overseeing the operation, USA Today reports. The 19 hijackers were led by Mohamed Atta, who piloted the plane that struck the North Tower.

Bin Laden went into hiding after 9/11 and was killed by US forces in Pakistan in 2011. Al-Zawahri died in a US drone strike in Afghanistan in 2022. Khalid Sheikh Mohammed remains held at Guantanamo Bay, where he and three co-defendants are due to face a military tribunal in 2028.

How many people died on 9/11?

A total of 2,977 people were killed in the attacks, not including the 19 hijackers, according to the 9/11 Memorial and Museum. It remains the deadliest attack by a foreign group ever carried out on US soil.

• World Trade Center: 2,753 deaths, including hundreds of first responders
• Pentagon: 184 deaths among passengers, crew and Pentagon staff
• Flight 93: 40 deaths after passengers fought back against the hijackers.

George W. Bush was serving his first term as president when the attacks happened. He was visiting an elementary school in Sarasota, Florida, sitting in on a reading lesson with students, when his chief of staff, Andrew Card, leaned in and told him that a plane had struck the World Trade Center. Bush briefly continued the classroom visit before being pulled away as the scale of the attacks became clear, and he addressed the nation later that day, USA Today notes.

Rudy Giuliani was mayor of New York City at the time. He became a national figure for helping lead the city through the immediate aftermath and the recovery effort that followed, earning the nickname “America’s Mayor,” according to USA Today.

How is New York marking the 25th anniversary today?

This year’s ceremony is the first that current New York City Mayor Zohran Mamdani will attend as mayor, and it has become tangled in political controversy. Giuliani publicly urged Mamdani, the city’s first Muslim mayor, not to attend this year’s commemoration, and made unfounded claims about Mamdani’s faith. Mamdani has said he intends to attend, as he did last year while still a state assembly member, describing 11 September as a day for the city to come together “not as individuals, but as New Yorkers.”

Ahead of the anniversary, Mamdani signed executive orders formally designating 11 September as a citywide “Day of Remembrance and Service” and announced steps to modernise the city’s emergency preparedness framework. His administration also released more than 170,000 pages of city records on the government’s response to the attacks, including material on air quality at Ground Zero, settling a long-running legal dispute with a 9/11 health advocacy group. Mamdani said the records showed New Yorkers were told the air was safe to breathe when it was not, adding that more FDNY members have since died from 9/11-related illness than were killed in the attacks themselves.

Twenty-five years later, the attacks continue to shape daily life in the US, from airport checks to security policy and public memory. As the anniversary approaches, ceremonies across the country will honour the victims and pass the story on to those born after 2001 who now make up close to a third of the US population, according to AP.