Commemorations will be held in the US today to mark the 19th anniversary of the 11 September terror attacks.
Almost 3,000 people were killed when hijackers crashed planes into the Twin Towers in New York, the Pentagon outside Washington DC and a field in rural Pennsylvania.
The US President Donald Trump and his Democratic opponent Joe Biden will pay separate visits to Shanksville, Pennsylvania, today to honour those who died.
A ceremony will be held today at the 911 Memorial in New York to mark the anniversary of the 2001 attacks.
The event will be attended by the US Vice President Mike Pence and by the Democratic presidential candidate Joe Biden.
Mr Biden will then travel to Shanksville where United Flight 93 crashed in a field on 11 September 2001.
In a separate visit, Mr Trump will also travel to Shanksville where he will attend a commemoration ceremony honouring the dead.