The World Trade Center south tower (L) bursts into flames after being struck by hijacked United Airlines Flight 175, as the north tower burns following an earlier attack, in New York City in this September 11, 2001 file photo. [Photo/Agencies]

For many in US, Sept 11, 2001, was a personal experience, an attack on their cities, on their homeland.

"Sept 11 is a monumental day in our nation's history, a significant day, and it obviously changed my presidency. I went from being a president that was primarily focused on domestic issues to a wartime president. It's something I never anticipated nor something I ever wanted to be."  ---George W. Bush.

The second tower of the World Trade Center bursts into flames after being hit by a hijacked airplane in New York in this September 11, 2001 file photograph. [Photo/Agencies]

"I had been in Chicago at the time, driving to a state legislative hearing downtown. The reports on my car radio were sketchy, and I assumed that there must have been an accident, a small prop plane perhaps veering off course. By the time I arrived at my meeting, the second plane had already hit, and we were told to evacuate the State of Illinois Building. Up and down the streets, people gathered, staring at the sky and at the Sears Tower. Later, in my law office, a group of us sat motionless as the nightmare images unfolded across the TV screen—a plane, dark as a shadow, vanishing into glass and steel; men and women clinging to windowsills, then letting go; the shouts and sobs from below and finally the rolling clouds of dust blotting out the sun."----Barack Obama.