A series of events will take place on Thursday in the United States to mark the 24th anniversary of the 9/11 attacks.
On Tuesday 11 September 2001, suicide attackers seized US passenger jets and crashed them into two New York skyscrapers, killing thousands of people.
The event had profound consequences across the globe.
Four planes flying over the eastern US were seized simultaneously by small teams of hijackers.
They were then used as giant, guided missiles to crash into landmark buildings in New York and Washington.
