The former Guantanamo guard, USA
Brandon Neely was a 21-year-old soldier in Texas's Fort Hood army base on the day of the attacks.
"In 2000 when USS Cole was hit by terrorists, there was outrage that President Clinton hadn't retaliated. With 9/11, I wanted to be part of a response.
"I hoped to be sent to Afghanistan but was told I was heading to Guantanamo Bay to run a detention facility.
"It was there where I started to change. The US had always been a standard-bearer of the way you treat people, and things didn't feel right.
"In the early days we were allowed to talk to detainees. The guards would make small talk, jokes and conversation. I met prisoners from Britain and we had things in common – Eminem, Dr Dre and clubbing. They seemed fine and I had to remind myself that there is no way we'd be locking up innocent people: they have to be guilty for something.
"I can't apologise for the government but I can apologise for my role in what happened.
"Things now have changed. Even Guantanamo prisoners who I've kept in touch with have told me it's time to make peace with the situation and move on. Two years ago I flew to London to meet some of the detainees I presided over at Guantanamo. Since then life has changed. I've been back to school, I've quit alcohol and I'm back in shape.
"Speaking out against American policy was the right thing to do. I sleep better at night, thinking I can't change the past – but at least now I'm making a difference to the future."
The student, France
Alissa Haddaji, a French Muslim now studying in the US, was 13 and living in Paris when she returned from school on 11 September.
"When I came home and switched on the television, I saw planes flying into buildings. I told my mother they were showing a great American action film on television. She looked utterly terrified. Disney had always led us to believe that America was an enchanting gateway to an idyllic life – but from that moment things changed. Politics was fiercely debated, and a surge of patriotism swept the country. I felt proud that we were not going to follow America into a war with Iraq.
"France felt independent of the world, assertive and powerful. Feeling that we could make a judicial assessment and stand against America gave us a sense of identity.
"But the hangover of that moment hasn't evaporated here in the US. I have heard the same jokes that France sucks and never wins wars.
"It was 11 September that ultimately made me decide to study American-French relations here at Brown University. Contrary to popular belief, the gap between France and the US has not narrowed even under President Obama; it is wider. But over time it will narrow again."
The bomb-blast survivor, Australia
Peter Hughes, 51, from Perth, was on holiday in Bali when terrorist bombs detonated there in 2002. He is now a motivational speaker advising people how to come back from adversity. He also runs a roofing business.
"It was evening in Australia and I was watching television when I saw the twin towers fall. It felt significant but not life-changing. I felt sympathy for the American people but far away from it all – and glad it was not happening to me.
"That changed a year later in Bali. I had gone to a nightclub after a few drinks. Through the alcoholic haze I [saw] an Indonesian boy with a backpack walking around the dancefloor – and I remember thinking it seemed unusual. Suddenly there was a loud explosion – the whole place went black and I thought a gas canister had exploded. I ran out of the nightclub, only to get hit by the car bomb about 30 metres away.
"9/11 came to mind, and I remember being unable to believe I had become ensconced in global terrorism. It brought home a new reality. I had never thought that Australians would be affected by what happened in New York.
"Since that moment my political views have hardened. I was staunchly in support of Bush going to war with Iraq, and John Howard's decision to support both Bush and Blair felt absolutely right. If anything, I think they should have gone in harder.
"Since 11 September, we have learned about how religion impacts on the world. We've discovered how low-life criminals can hijack a religion, and make it seem right, when, actually, they're wrong. Individuals' actions can stain an entire religion. But there's a lot more of us than there are of them; hopefully the world is ultimately a better place for what we have learned."
The grieving sister, United Kingdom
Esther Hyman, 42, lost her younger sister, Miriam, during the 7/7 bombings in London. She was in Oxford on 11 September.
"Like everyone, I watched in shock and disbelief. I remember going out for lunch and by the time I came back, the towers had collapsed. I had already booked a holiday to New York before the attacks and three weeks later I went out. It was pretty spooky. I visited Ground Zero; the air was still thick and tributes and pictures were littered everywhere.
"My family was saying sooner or later it was bound to happen here... but we never imagined our family would be so affected.
"Miriam protested against our involvement in the war. I have come to believe what happened to her was a direct result of our foreign policy and those young people being radicalised by our involvement. Now I work almost full-time for the Miriam Hyman Memorial Trust, which provides eye-care service provision in India. I think every individual who benefits from the eye surgery there helps to counteract the negative events of 7/7 and the aftermath of the 11 September bombings."
Vishnu Dattaram Zende
The pragmatist, India
Vishnu Dattaram Zende, 41, is a station announcer at CST Railway Station in Mumbai. He was on duty when gunmen opened fire during the Mumbai terror attacks.
"On 11 September, I had just got home from work where our TV is always on in the background. It was then that I saw the planes flying into the buildings.
"My first reaction was anger. If someone gets hurt, I feel that hurt. But in such a large-scale event like 9/11 how many families can one truly think of? It was overwhelmingly painful.
"Gradually, you get back to routine. And I thought things were fine until India came under attack. On 11 September no one expected planes to fly into buildings. And on 26 November, no one expected hotels under siege and gunmen running riot across Mumbai... Nothing is unimaginable any more.
"My main message to friends is to stay alert – we need to be cleverer than terrorists. This Sunday I will be on duty at the station and my job is to keep people alert to terrorist threats. That's always been my job, but the events of the last 10 years have made it all the more important."
The extradited executive, Canada
Maher Arar has Canadian-Syrian citizenship. In 2002 he was arrested at New York's JFK airport and extradited to Syria for more than a year, where he says he was tortured.
"On 11 September, I was consulting for a Boston-based company and had just arrived in San Diego. My colleague was Jewish and I am Muslim and we used to make jokes about Israel and Palestine. That morning he phoned me and told me of the attacks. But I didn't believe him until I switched on the television.
"I remember the day I was held in transit in JFK, New York. I went through immigration, where I was told to wait while the FBI arrived and said they wanted to ask questions. But I was never told what it was about. I was interrogated for eight hours and was taken to the Metropolitan Detention Center in New York.
"Shortly afterwards I was put on a private jet to Syria. The journey felt like a dream, I was thinking how to avoid torture in Syria while questioning my own beliefs about Western democracies.
"Had it not been for the campaigning efforts of my wife, Monia, my case could very easily have gone unnoticed by media and government.
"My experience opened me up to more in life – I value human rights more and care more about what happens in the world. I now know how important it is not to take your rights to freedom for granted. People have to make democracy work – if you trust the government blindly, you're never going to be safe."
The ferryman, Afghanistan
Rasheed Jalawan is a ferryman from L'Alpur, Afghanistan, who escorts people across the Kabul River. During the war in Afghanistan he was made to help al-Qa'ida members to leave the country for Pakistan. He features in al-Jazeera's documentary The 9/11 Decade.
"People talk about the time after 11 September, but the poor people in Afghanistan have always had it tough. The time after the revolution was some of the bloodiest. In President Karmal's time this place was under bombardment. Bombs were thrown on the village and houses were set on fire.
"During the first days of the American invasion, many of the Taliban and Arabs escaped out of Afghanistan. The Taliban would stop our ships and make us escort them across the river and into Pakistan.
"I remember once there was a guy praying nearby, and when I looked at him I thought it could have been Osama bin Laden. I can't say anything on his death. I just pray that God helps all the Muslims, may God never bring shame on the grave of our Prophet, because our religion is very beautiful.
"But in recent years some things have strayed away. May God help to bring us back on the right path."
Abdulaziz Al Rabah
The new Arab youth, Saudi Arabia
Abdulaziz Al Rabah was 13 when the twin towers fell. He watched the attacks unfold from his home in Hafar Al-Batin. He is now a journalist.
"I remember watching the attacks on television. We didn't know who did it. I had always thought that the Americans had done great work; I couldn't understand why some people in my country were so happy at the time of the attacks. Finding out that so many of the hijackers were Saudis I felt ashamed.
"The event shaped young people. Usually by your teens you would be more attracted to novels and comics, but there was suddenly a hunger for politics, news and information from sources outside Saudi Arabia. People started devouring newspapers.
"Some people use their money to support al-Qa'ida and terrorist organisations around the world, but after 9/11 people became far more aware and questioning. You can see the effect of that with the Arab Spring. This new generation is well connected, and I feel hopeful that the next 10 years will be more peaceful than the last."
The Guantanamo detainee, Libya
Omar Deghayes was born in Libya but was living in Afghanistan on the day of the attacks. Now a British citizen, he was picked up in Pakistan in 2002 and imprisoned in Guantanamo; he says he was tortured there.
"On 11 September, I had just got married and had been living in Afghanistan for about three years. I was working with NGOs doing relief work and had opened a law practice, as well as imports and exports to Pakistan.
"At first we thought it would be the standard American response of cruise missiles, no one thought it would be an invasion. I moved my family out of Kabul and into Pakistan, where it seemed safer. But in 2002 our villa was stormed by militia who put black bags on our heads. I wasn't even interrogated, just moved from a prison in Lahore to Islamabad and then on to Bagram air base, where I was handed to the Americans [and] put in a cargo plane and flown to Guantanamo Bay. Our eyes were covered and I remember losing all senses as we travelled on the plane.
"We were innocent people who did not contribute to 11 September and were thousands of miles from New York when it happened.
"I am no longer the same person. I have a much larger distrust of people and we don't trust politicians, neither American nor Arab. There is a new coldness and mistrust that will take a long time to shake off."
The reconstructor, Iraq
Saad Saraf moved to Britain in the 1970s. In the wake of the Iraq war he formed the International Council of Iraqi Experts, a rebuilding programme, and is chief executive of Mediareach, a marketing company for multicultural communities.
"I remember the response on 9/11 from Iraq. There was still a hangover from the first Gulf war. I had always been struck by the picture of George Bush Snr on the floor of the Rashid Hotel in Baghdad. It had been removed by American generals when I returned to the hotel just after the war.
"My family were delighted when the Iraq war happened, as were many who were living under the oppression of the Saddam Hussein regime. We used to say the Americans brought him in and only the Americans can take him out.
"When America invaded, Iraqis did not know how to respond, they had a decade of Saddam whipping up anti-US propaganda and felt frightened and confused. Shias and Kurds were generally delighted, but the Americans made lots of mistakes... Ultimately, though, the benefits of democracy have outweighed that.
"I think the Arab Spring is symptomatic of a new way of life that is spreading across the Middle East. I remember my dad telling me: 'Sometimes I wake up, and think is this real or am I still dreaming? We are no longer living under Saddam. The nightmare is over.'"
The pacifist, Spain
Beatriz Alegre was a 21-year-old student in Valencia and having lunch with her family at the time of the 9/11 attacks.
"I was watching the news and couldn't believe it. It took about 10 minutes to see what we were looking at. On 11 September it was too far away. But [even so] in Spain we started being more careful and looked at Arab people more suspiciously.
"But the Madrid bombs changed the country. Everyone thought it was ETA and could not imagine it could be foreign-born bombers, and then Spain's confidence was shattered. Until then we had thought that we were a country which had not ever offended anybody.
"Time is the ultimate healer. I'm now more careful about giving information to other people. Events are more carefully organised and there is far more security. Most of all, our confidence has been shaken – we had always thought we were impervious to global terrorism. Now we all share a far greater sense of global empathy."
Additional reporting: Sarah Morrison and Holly ChristodoulouReuse content