Memorial services are being held today in the United States and other parts of the world to mark the 25th anniversary of the September 11, 2001 terrorist attacks.
A total of 2,977 people were killed when hijackers crashed three passenger planes into the World Trade Center in New York City and the Pentagon in Virginia.
A fourth hijacked aircraft crashed into a field in Pennsylvania after passengers attempted to overpower the attackers.
Memorial services are taking place at the three crash sites in New York, Virginia and Pennsylvania to honour the victims.
An event to commemorate the victims is also being held at Queen Elizabeth Olympic Park in London.
