Twelve years have gone by since terrorists attacked the World Trade Centre (WTC) that killed 2,753 people. Observances have been planned on the site of the disasters. Every year the family members of the victims of the 2001 and the 1993 attacks, read the names of their loved ones at a ceremony held at the 9/11 Memorial plaza.
Moments of silence are marked at 8.46 am, the time of the first impact and 9.03 am crash of the United Airlines Flight into the WTC south tower.
The 9/11 attacks had killed 2,753 whereas the 1993 bombings had killed six people.
Families to read out names of their dear ones
At the Pentagon, where the American Airlines Flight 77 crashed at 9.37 am on the same day killing 184 people, President Obama will speak to the family members of those who died, at the private observance.
In southwestern Pennsylvania, a wreath will be laid and the names of the 40 people, who died, will be read. United Airlines Flight 93 had crashed here at about 9.45 am. Though the target of these hijackers is not known, it is alleged that the hijackers feared attacks from the passengers and the crew and crashed the plane in a field.