Sept. 11: Former first lady Laura Bush, from left, former President George W. Bush, first lady Michelle Obama and President Obama hold hands to their hearts during the national anthem as friends and relatives of the victims of 9/11 gather for a ceremony marking the 10th anniversary of the attacks at the National September 11 Memorial at the World Trade Center site. (AP)
Sept. 11: A girl, center, cries before reading her father's name as the victims of 9/11 are remembered during a ceremony marking the 10th anniversary of the attacks at the National September 11 Memorial at the World Trade Center site. (AP)
Sept. 11: New York Firefighter Zachary Fletcher embraces his mother Monica Fletcher after finding his twin brother Andre G. Fletcher's name engraved at the south pool of the National September 11 Memorial. (AP)
Sept. 11: Celeste Pocher embraces her daughter after finding her brother in law's name, John Pocher at the north pool at the National September 11 Memorial. (AP)
Sept. 11: Family of 9/11 victims read the names of those killed in the World Trade Center during a ceremony marking the 10th anniversary of the attacks at the National September 11 Memorial at the World Trade Center site in New York. (AP)
Sept. 11: Rita Agnelo touches the name of her son, Joseph Agnelo, who was killed on during the Sept. 11, 2001 World Trade Center attacks, as she attends 10th anniversary ceremonies at the in New York. (AP)
Sept. 11: The World Trade Center Flag is presented as friends and relatives of the victims of 9/11 gather for a ceremony marking the 10th anniversary of the attacks at the National September 11 Memorial at the World Trade Center site in New York. (AP)
Sept. 11: People gather during a ceremony marking the 10th anniversary of the attacks on the World Trade Center outside the World Trade Center site in New York. (AP)
Sept. 11: Vice President Joe Biden, from right, Defense Secretary Leon Panetta, and Chairman of the Joint Chiefs of Staff Adm. Mike Mullen participate in commemorative ceremony to honor vicitms of the Sept. 11 attacks during the 10th anniversary at the Pentagon in Washington. (AP)
Sept. 11: Families and survivors honor the victims of the the Sept. 11, 2001, attack on the Pentagon at a tenth anniversary remembrance ceremony at the Pentagon Memorial in Washington. (AP)
Sept. 11: An honor guard plays Taps at the the Pentagon Memorial as the 10th anniversary of the September 11 attacks are observed at the Pentagon in Washington.
Sept. 11: Matthew Bowman, with the honor guard, carries a wreath to be placed near fragments of steel from the World Trade Center towers during a remembrance ceremony at the Garden of Reflection in Yardley, Pa. (AP)
Sept. 11: President Obama and first lady Michelle Obama place a wreath at the Flight 93 National Memorial Sunday in Shanksville, Pa. (AP)
Sept. 11: Pennsylvania Gov. Tom Corbett, left walks with his wife Susan after viewing the Wall of Names near the crash site of Flight 93 in Shanksville, Pa. (AP)
Sept. 11: President Obama and first lady Michelle Obama walk to the crash site of Flight 93 during their visit to the Flight 93 National Memorial. (AP)
Sept. 11: President Obama and first lady Michelle Obama place a wreath at the Flight 93 National Memorial Sunday in Shanksville, Pa. (AP)
Sept. 11: Pennsylvania Gov. Tom Corbett, left walks with his wife Susan after viewing the Wall of Names near the crash site of Flight 93 in Shanksville, Pa. (AP)
Sept. 11: President Obama and first lady Michelle Obama walk to the crash site of Flight 93 during their visit to the Flight 93 National Memorial. (AP)