9/11: Iconic images

The second tower of the World Trade Center bursts into flames after being hit by a hijacked airplane in New York September 11, 2001. REUTERS/Sara K. Schwittek

Then President George W. Bush listens as White House Chief of Staff Andrew Card informs him of a second plane hitting the World Trade Center while Bush was conducting a reading seminar at the Emma E. Booker Elementary School in Sarasota, Florida, September 11, 2001. REUTERS/Win McNamee

People look out of the burning North tower of the World Trade Center in New York City September 11, 2001. REUTERS/Jeff Christensen

Television image of a body falling from one of the towers of New York's World Trade Center, following a fire caused when two hijacked airliners were crashed into the buildings, September 11, 2001. REUTERS/TV

Pedestrians react to the World Trade Center collapse September 11, 2001. REUTERS/Stringer

The remaining tower of New York's World Trade Center, Tower 2, dissolves in a cloud of dust and debris about a half hour after the first twin tower collapsed September 11, 2001. REUTERS/Ray Stubblebine

A rescue helicopter surveys damage to the Pentagon as firefighters battle flames after a hijacked airplane crashed into the U.S. military headquarters outside of Washington, September 11, 2001. REUTERS/Larry Downing

Rescue workers carry mortally injured New York City Fire Department chaplain, the Rev. Mychal Judge, from the wreckage of the World Trade Center in New York City September 11, 2001. The Chaplain was crushed to death by falling debris while giving a man last rites in the trade center. REUTERS/Shannon Stapleton

A group of firefighters walk amid rubble near the base of the destroyed south tower of the World Trade Center in New York September 11, 2001. REUTERS/Peter Morgan

The wreck of the World Trade Center smolders in the background as a man passes a subway stop near ther World Trade Center Towers after planes crashed into each of the buildings in New York on September 11, 2001. REUTERS/Peter Morgan

An American flag flies near the base of the destroyed World Trade Center in New York, September 11, 2001, taken after the collapse of the towers. REUTERS/Peter Morgan

The damaged area of the Pentagon building, where a commercial jetliner slammed into it September 11, is seen in the early morning at sunrise with the U.S. Capitol Building in the background, September 16, 2001. REUTERS/Larry Downing

A New York City fireman calls for more rescue workers to make their way into the rubble of the World Trade Center September 15, 2001. REUTERS/U.S. Navy Photo by Journalist 1st Class Preston Keres/Handout

Then President Bush is shown with retired firefighter Bob Beckwith (R) at the scene of the World Trade Center disaster on September 14, 2001. REUTERS/Win McNamee

New York police stand near a wanted poster printed by on a full page of a New York newspaper for Saudi-born militant Osama bin Laden in the financial district of New York, September 18, 2001. REUTERS/Russell Boyce

A lone police officer sits away from where family members of the victims of the September 11 attacks on the World Trade Center were gathering at the base of the "Ground Zero," September 11, 2002. REUTERS/Mike Segar

Courtney Ball, 19, of Sommerville, New Jersey, cries at the Flight 93 Temporary Memorial just outside Shanksville, Pennsylvania, September 11, 2005. REUTERS/Jason Cohn

A man grieves outside the World Trade Center site in New York September 11, 2006. REUTERS/Shannon Stapleton

A picture of a person who died in the September 11th attacks at the World Trade Center are seen on a fence at the site in New York, May 3, 2011 after U.S. forces killed al Qaeda leader Osama Bin Laden in Pakistan. REUTERS/Shannon Stapleton

A reflection can be seen on a glass barrier in the Top Of The Rock observation deck in front of the Tribute in Light memorial shining behind the Empire State Building marking the ninth anniversary of the September 11 attacks on the World Trade Center in New York September 11, 2010. REUTERS/Lucas Jackson