A quarter of a century after hijacked planes struck New York, Washington and Pennsylvania, the attacks of 11 September 2001 remain lodged in the American psyche more firmly than almost any other event of the past 25 years.
A new Ipsos poll finds that roughly half of US adults, unprompted, name 9/11 among the most significant events of their lifetime — ahead of the Covid-19 pandemic, the elections of Barack Obama and Donald Trump, and Hurricane Katrina of 2005.
Nine in ten say the attacks changed the country "a great deal" or "quite a bit," and most Americans can still recall exactly where they were when they heard the news.
Yet despite that lasting wound, only around one in ten plan to actively mark Friday's anniversary - for those that do a moment of silence and the flying of the flag are the most common gestures.
Confidence in the government's ability to prevent another attack has also declined steadily since the record highs recorded in the days after 2001.
What's planned for the 25th anniversary?
Commemorations will unfold across the three sites. In New York, victims' relatives will gather on the Memorial plaza to read aloud the names of those killed, punctuated by seven moments of silence — one more than in previous years, added to honour those who have since died of 9/11-related illnesses.
Ceremonies will also take place at the Pentagon in Arlington and at the Flight 93 National Memorial in Shanksville, Pennsylvania.
Trump will not attend the New York ceremony this year, opting to speak at the Pentagon instead.
Vice President JD Vance will go to Ground Zero - the area where the first search for survivors in began - while former presidents Joe Biden, Barack Obama, Bill Clinton and George W. Bush are also expected to attend the New York event.
Why is it called 9/11?
For some, the shorthand can seem puzzling. The date was the eleventh day of the ninth month but the American convention of writing dates with the month-first leads to "9/11" which also mirrors how the emergency number 911 is dialled in the US.
How many Europeans died in 9/11?
While nearly 3,000 Americans died in the event, hundreds of foreign nationals were also among the dead. Estimates place the number of non-American victims at roughly 372, drawn from around 60 countries.
Britain suffered the heaviest toll of any country besides the US, with 67 nationals killed. Germany, Italy, Ireland and other European states also lost citizens, many of them financial workers employed at or visiting the World Trade Center.
American financial services firm Cantor Fitzgerald occupied floors 101 through 105 of the World Trade Center's North Tower, directly above the impact zone of American Airlines Flight 11.
The company employed a number of Europeans and in total 658 employees were killed that day - the largest loss of life of any individual firm.
Number of Europeans killed in 9/11 attacks:
- United Kingdom — 67
- Germany — 11
- Italy — 10
- Ireland — 6
- Poland — 6
- Portugal — 5
- France — 4
- Romania — 4
- FR Yugoslavia (Serbia and Montenegro) — 2
- Sweden — 2
- Switzerland — 2
- Belarus, Belgium, Lithuania, Moldova, Netherlands, Russia, Spain, Ukraine - 1 per country
What happened to the perpetrators?
All 19 hijackers died carrying out the attacks - 15 were Saudi nationals, two from the United Arab Emirates, and one from Egypt and one from Lebanon.
Behind them stood the wider terrorist al-Qaeda network who claimed direct responsibility for the attacks. Osama bin Laden, the group's leader, evaded capture for almost a decade before being killed by US special forces in Pakistan in 2011.
His eventual successor, Ayman al-Zawahiri, was killed in a drone strike in Kabul in 2022.
The self-described "mastermind" of the plot, Khalid Sheikh Mohammed, was captured in Pakistan in 2003 and has been held at Guantánamo Bay since 2006 charged with the first-degree murder of 2,977 people.
A US military judge has now set his long-delayed trial to begin in June 2028, alongside several alleged co-conspirators, following a collapsed 2024 plea deal that would have seen the men admit guilt in exchange for the death penalty being removed from sentencing options.
Proceedings have dragged for over two decades amid disputes over evidence obtained through the use of torture, including waterboarding, at secret CIA sites.
