It has been a year since the world was stunned by images of two commercial planes crashing into the twin towers of the World Trade Centre in New York City.

For many, it looked too dramatic to be real. But just as the world came to grips with the reality, another plane ploughed into the Pentagon and yet another crashed to the ground in Shanksville, Pennsylvania.

Close to 3,000 lives were lost in the tragedy, from passengers in those ill-fated flights to rescue workers.

The days, weeks and months which followed were filled with questions that needed to be answered. Why? Why this systematic attack on America? What was the agenda?

Soon enough, Osama Bin Laden was the name on everyone's lips as he became America's public enemy number one as US officials identified his as the mastermind behind the attacks.

As survivors and families and friends of those who perished deal with the tragedy and pick up the pieces of their lives, we look back at the tragedy that was September 11.