9/11 Ten years on: Your global stories
Ten years ago, 19 hijackers took control of four passenger jets, aiming to fly them into buildings in New York and Washington.
The twin towers of the World Trade Center in New York were hit and destroyed by two planes, while the Pentagon near Washington was badly damaged by another. A fourth plane crashed in rural Pennsylvania after passengers fought back against the hijackers.
The attacks on 11 September 2001 ended many lives and changed countless others, and the ramifications are still felt in the way we lead our lives today.
BBC News website readers from countries around the world have been telling us their memories of 9/11, and how the event has affected them personally.
Mohamed Safi, 30, radio presenter, Cairo, Egypt
That day was traumatic for me. I was literally packing my bags to head to the States with my ticket booked for 12 September.
I was halfway through my medical studies and decided to take a year off as I was offered a job as an editor for an Arabic comics publisher in the US.
Like any household in the world, ours was full of shock and horror at the images I was seeing on TV. I remember thinking about people's families and what they must be thinking.
Everyone's life on the planet instantly changed that day, mostly for the worse.
The true, dark head of radicalisation instantly became evident to all. My plans of living and working in the US were dealt a massive blow.
Ten years on, being a Muslim called Mohamed is still cause for alarm for many Westerners. It became more and more important for me to deliver the message that this is not Islam.
Miche Norman, 49, accountant, Hod Hasharon, Israel
I was doing reserve duty in the West Bank when my mother called from the UK asking if I had heard from my brother-in-law. He was working in the World Trade Center. All phone lines between the US and the UK were down.
So I found myself worrying about my brother-in-law, and watching as Palestinians hooted car horns and handed out trays of sweets.
I didn't see any of the images that day but I could imagine the scene from what I heard.
We're used to the threat from terrorism in Israel. But the scale of this was numbing. I think it changed perceptions in other parts of the world - suddenly nothing was beyond reach.
We finally got hold of my brother-in-law about eight hours later. He had been in building seven. Initially they were told not to leave - he was there to see the second plane hit the South Tower.
Flash Weldon, 56, technical writer, Bern, Switzerland
I was at work in an office in Hamburg at the time. Several of my colleagues had news programmes on their computers - and they called me over to look at what was happening.
I remember staring at those images. We were a polyglot group of American, Germans, Brits - even Iranians. We forgot who was of what nationality and were just transfixed by the incomprehensible horror of it.
When the Pentagon was struck I recalled Pearl Harbor and President Roosevelt's phrase about that day being a date which will live in infamy.
Initially I received a great deal of sympathy from people because I was an American. But that changed two years later, after America invaded Iraq. After that I met people who would refuse to talk to me.
Now I feel that security measures have increased so much that I can no longer travel to my former homeland without being treated as a terrorist suspect. Being photographed and fingerprinted at the border is totally unacceptable.
Christian Ghisays, 48, artist, Ocho Rios, Jamaica
The day of the 9/11 attacks, I was moving house and just happened to hear the news on the BBC World Service.
So I unloaded the TV just in time to see the second plane crash like a fireball into the South Tower. It felt like Armageddon.
It was just so shocking and painful to see the loss of so many innocent lives. And the fact that it happened in the heart of America was even more shocking.
It was as if America lost its innocence that day.
I think that day affected everybody, certainly there was nothing like that in my life before. It makes you realise what terrible things are possible.
Since this tragic day, the world has seen the effects of wars and loss of compassion. Relations between nations have got worse.
For travellers, you find yourself facing constant security checks and hassled like you are a nonentity.
Terry Norton, 57, local council worker, Nantucket, Massachusetts, US
I was a driver for a shuttle bus ferrying people to the Pentagon on that day. By 09:30 in the morning I had heard about the events in New York.
I remember turning in my seat and then saw a plane framed in an overpass that connects a car park with the Pentagon.
I started thinking about many things at once in a flash of a second. I grabbed the bus radio and screamed: "Oh my God, there is another one happening here!"
I felt the shockwave. The next moment I was running towards the Pentagon. I don't know why. Part of me couldn't believe it had actually happened. I could see the tail of the plane sticking out from the building covered in flames, and I knew all the people on board were dead.
I'm still trying to come to terms with those events. Why was I spared? If I had left a few minutes earlier my bus could have been hit.