Photos: 9/11 observance ceremonies | 13 years later

A woman places flowers in the inscribed names of victims along the edge of the North Memorial Pool during observances on the 13th anniversary of the Sept. 11 terror attacks on the World Trade Center in New York.  (Justin Lane / Associated Press)

A man kneels before the Fire Department of New York Memorial Wall, dedicated to firefighters lost on 9/11, on Liberty Street near the World Trade Center site.

A woman gazes at the sky during memorial observances held on the 13th anniversary of the 9/11 terror attacks at the World Trade Center site in New York.

Former New York Mayor Rudolph Giuliani traces with his finger the letters of a name etched into the rim of the North Memorial Pool during 9/11 anniversary observances at the World Trade Center site.

President Obama bows his head during a moment of silence at the Pentagon during a ceremony to mark the 13th anniversary of the 9/11 attacks.

President Obama, First Lady Michelle Obama and Vice President Joe Biden are joined by a military color guard and White House staff on the executive mansion’s South Lawn as Taps is played after a moment of silence marking the 13th anniversary of the 9/11 attacks.

President Obama, left, Defense Secretary Chuck Hagel and Joint Chefs Chairman Gen. Martin Dempsey lead a ceremony at the Pentagon to mark the 13th anniversary of the 9/11 attacks.

An American flag flies at half-staff in front of workers on scaffolding at the U.S. Capitol building on the 13th anniversary of the 9/11 terror attacks.  (Michael Reynolds / EPA)

Clouds roll over 1 World Trade Center, left, seen from the Heights neighborhood of Jersey City, N.J., at sunrise on Thursday.

One column of the Tribute in Light, representing the World Trade Center’s Twin Towers, beams into the Manhattan sky during a test last year.  (Mark Lennihan / Associated Press)