Thursday marks the seventh anniversary of the September 11, 2001 terrorist attacks on the United States.
Ceremonies are planned across the country to honor the victims. Nearly 3,000 people were killed when hijackers crashed four commercial planes into the twin towers of New York's World Trade Center, the Pentagon in Washington and a field in Pennsylvania.
A moment of silence at 8:46 am EST will mark the point when the first plane hit the World Trade Center's North Tower.
U.S. President George Bush will deliver remarks later Thursday morning at the unveiling of a memorial to honor the 184 people who died at the Pentagon.
U.S. presidential candidates John McCain and Barack Obama will also participate in events. Obama will attend a ceremony near the World Trade Center site, while McCain will attend a ceremony in Pennsylvania.
Both candidates will later speak in New York City at a nonpartisan "ServiceNation Summit" forum to address the events of September 11 and the importance of national service.
Thursday's ceremonies will include the reading of the victims' names.
Earlier this week a memorial honoring the victims of the terrorist attacks was dedicated at Boston's Logan International Airport. The airport was the departure point of two of the hijacked flights.
