US President Joe Biden attended a ceremony in New York today to mark the 20th anniversary of the September 11th attacks.
Nearly 3,000 people were killed when Al Qaeda hijacked four passenger planes.
Two were flown into the Twin Towers in New York and a third was crashed into The Pentagon.
The ceremony at ground zero was started by a choir singing the American national anthem, followed by a minute's silence.
The relatives of the victims read out the names of every person who lost their lives and bells tolled at the exact moment the jets hit the twin towers.
On the 20th anniversary of 9/11, we honor the lives lost and the first responders who ran towards danger to save others during the worst terrorist attack on America in our history. They remind us that the strength of the human spirit knows no bounds.
— Kamala Harris (@KamalaHarris) September 11, 2021
The fourth jet, flight 93, was taken down by the crew and passengers on board in a field in Pennsylvania, 44 people died.
US Vice President, Kamala Harris, spoke today at a memorial event in Pennsylvania:
"On this solemn day of remembrance we must challenge ourselves, to look back, to remember. We must also look forward the future because in the end I do believe that is what the 40 were fighting for."