A test of the Tribute in Light rises above lower Manhattan, on September 6, 2011, in New York City. The memorial, sponsored by the Municipal Art Society, will light the sky on the evening of September 11, 2011, in honor of those who died ten years ago in the terror attacks on the United States. (AP Photo/Mark Lennihan)

French President Jacques Chirac carries a bouquet of flowers towards a makeshift memorial to the victims of the terrorist attack on the World Trade Center at Union Square in New York, on September 19, 2001.(AP Photo/Roberto Borea) #

People stop to look at posters of missing people on the wall of The Famous Ray's Pizza in Greenwich Village in New York, on September 14, 2001. This wall, and many others around the area, was covered with posters of people missing after the collapse of the World Trade Center. (AP Photo/Beth Keiser) #

A jet takes off from the flight deck of the aircraft carrier USS Enterprise in the Persian Gulf, on October 11, 2001. After the refusal of the Taliban regime to stop harboring al-Qaeda, the U.S. government launched military operations on October 7, 2001. (Reuters/Jockel Finck) #

An Afghan Northern Alliance fighter stands guard on a rooftop as plumes of smoke rise from Taliban positions after a US air force B-52 bombed the area in Moshin-Ab and Karabakh some 35 km North of the Afghan capital Kabul, on November 2, 2001. B-52's heavily bombed front line Taliban positions pounding the hardline Islamic movement in some of the heaviest strikes of the campaign so far. (Reuters/Yannis Behrakis) #

A group of Western soldiers unload their equipment from a military truck escorted by members of Afghanistan's opposition Northern Alliance, near the Imam Sahib front, near Khoja Bahawuddin town in northern Afghanistan, on November 10, 2001. (Reuters/Recai Komur-Sabah News Agency) #

A combination of pictures created on September 9, 2011 shows (left) a Northern Alliance soldier (mujahedeen) standing in front of a mortar arsenal left behind by the Taliban militia at Ekhtiareddin castle in Herat, where the Northern Alliance were holding Taliban militia as prisoners of war, on November 16, 2001, and (right) an Afghan policeman standing in the same spot where the Taliban arsenal used to be on August 23, 2009. 10 years later, Herat, close to the Afghan border with Iran, is seen as one of the safest parts of Afghanistan and was among the first wave of seven places that passed from foreign to Afghan security control in July, 2011. (Behrouz Mehri/AFP/Getty Images) #

Two photographs show 23-year-old US Crew Chief Spc. Stephen Culver (right) from the Medevac unit of the 159th Brigade Task Force Thunder resting after a mission at Forward Operating Base (FOB) Pasab in Kandahar province, Afghanistan, on August 28, 2011, and a photograph of him (left) taken ten years earlier when he was 12, posing for a portrait at Hudson Middle School in Sachse, Texas during the beginning of the sixth Grade in August, 2001. (Johannes Eisele/AFP/Getty Images) #

Stars form trails in the sky during a long time-exposure of a watchtower at Forward Operating Base Kuschamond in Paktika province on September 6, 2011, a decade after the attacks of 9/11. Of 100,000 US troops in Afghanistan, 33,000 will leave by mid-2012, even as a still-potent Taliban insurgency is focused on headline-grabbing suicide attacks against government officials and foreign targets. (Johannes Eisele/AFP/Getty Images) #

In March of 2003, before the invasion of Iraq, Callie Gates (left) of Boston, Massachusetts, and Amelia Rutter (right) of Minneapolis, Minnesota, sing during an anti-war candlelight vigil at the Lincoln Memorial in Washington, D.C. Photo taken on March 16, 2003. The U.S. administration was preparing for a pre-emptive attack on Iraq, with the intent of removing Saddam Hussein and neutralizing weapons of mass destruction that were believed to be there. No such weapons were ever found. (Alex Wong/Getty Images) #

Lieutenant General Jeff Conaway (center), Commanding General of the 1st Marine Expeditionary Force addresses the British troops on March 14, 2003 in Northern Kuwait. The troops were preparing for possible action against Iraq. (Cpl Paul Jarvis/MOD/Getty Images) #

At the bomb dump at an air base in the Persian Gulf, messages are written by military personnel on Guided Bombed Units, (G.B.U.-10) 2000 pound, and Joint Direct Attack Munition (J.D.A.M) Mark 84, 2,000 pound bombs as they sit ready for use as American forces get ready for a possible war with Iraq, on March 15, 2003. At the time, there was a belief among some that Saddam Hussein had supported al-Qaeda and bore some responsibility for the attacks of 9/11. The Senate Select Committee on Intelligence issued a 2006 report that concluded, in part, that there was no evidence of ties between Hussein and al-Qaeda. (Paula Bronstein/Getty Images) #

Smoke covers the presidential palace compound in Baghdad on March 21, 2003 during a massive US-led air raid on the Iraqi capital. Smoke billowed from a number of targeted sites, including one of President Saddam Hussein's palaces, an AFP correspondent said. Western Coalition forces overtook the country in less than two months, but sectarian violence and insurgent attacks have made rebuilding efforts extremely difficult over the past eight years. (Ramzi Haidar/AFP/Getty Images) #

This image, copyright owner unknown, obtained by the Associated Press from an Arab language web site, and seemingly shot on a cell phone camera appears to show former Iraqi leader Saddam Hussein just prior to his hanging in Baghdad early Saturday, December 30, 2006. (AP Photo) #

Eight years after the initial invasion of Iraq, U.S. Army soldiers from D Co., 1st Battalion, 18th Infantry Regiment, confer during a patrol outside Contingency Operating Site Taji, north of Baghdad, on Sunday, August 7, 2011. (AP Photo/Maya Alleruzzo) #

Three of the architects of the attacks of 9/11. (Top) Osama bin Laden is shown watching himself on television in this video frame grab released by the Pentagon on May 7, 2011. Five videos were found in bin Laden's compound in Abbottabad, Pakistan after U.S. Navy Seals stormed the compound and killed bin Laden. (Left) Khalid Sheikh Mohammed, during his arrest in Rawalpindi, Pakistan, on March 1, 2003. Mohammed has been in U.S. custody since 2003, and will face a military trial at the Guantanamo Bay detention facility, charged with 2,973 individual counts of murder among other crimes. (Right) Al Qaeda's former second-in-command (now top commander) Ayman al-Zawahri speaks from an unknown location, in this still image taken from video uploaded on a social media website on June 8, 2011. Osama bin Laden's longtime lieutenant said the United States faces rebellion throughout the Muslim world after killing the al Qaeda leader, according to a 28-minute YouTube recording. In what appeared to be his first public response to bin Laden's death in a U.S. commando raid in Pakistan, the Egyptian-born Zawahri warned Americans not to gloat and vowed to press ahead with al Qaeda's campaign against the United States and its allies. (Reuters/Pentagon - Reuters/Courtesy U.S.News & World Report - Social Media Website via Reuters) #

Members of the public react as they walk past a New York Police Department Hercules team on patrol near Penn Station in New York August 24, 2011. NYPD Hercules teams patrol through New York making multiple appearances around the city each day at locations that are decided either in response to specific intelligence or simply to provide a show of force at high-profile sites. The police department has worked since 9/11 on a long-term project to permanently increase vigilance in Lower Manhattan and Midtown, home to prominent financial institutions and national landmarks. (Reuters/Lucas Jackson) #

A New York City Fire Department engine recovered from the World Trade Center disaster site sits inside Hangar 17 at New York's John F. Kennedy International Airport, on June 16, 2011. A program operated by the Port Authority of New York and New Jersey, The World Trade Center steel program, is selecting portions of the steel recovered from the World Trade Center and donating it to cities, towns, firehouses and museums around the U.S. and the world who request it for use in 911 memorial sites in time for the 10 year anniversary of the 2001 attacks. (Reuters/Mike Segar) #

Construction workers shape a steel form for the foundation of the World Trade Center transportation hub, on Wednesday, August 31, 2011 in New York City. (AP Photo/Mark Lennihan) #

A view of the World Trade Center construction site and the National September 11th Memorial and Museum in New York's lower Manhattan, on August 24, 2011. New York will mark the 10th anniversary of the attacks on the World Trade Center with ceremonies on September 11. (Reuters/Lucas Jackson) #

A man photographs the One World Trade Center tower, which is under construction, from a window at the World Financial Center's Winter Garden in New York, on July 20, 2011. (Reuters/Mike Segar) #

The sun sets over Jersey City and the World Trade Center site, with One World Trade Center to the right on August 28, 2011 in New York City. (Chip Somodevilla/Getty Images) #

Ivy Preparatory Academy sixth graders Simin Savani, left, and Hannah Baker, right, watch a news reel of the 9/11 terrorist attacks in school in Norcross, Georgia, on May 4, 2011. Educators are finding it more difficult each year to teach about September 11, 2001, as students remember less and less -- or nothing at all -- about the terrorist attacks. (AP Photo/David Goldman) #

In a cemetery outside Vilnius, Lithuania, Vladimir Gavriushin sits at the grave he built for his daughter Yelena on July 25, 2011. Yelena was one of the nearly 3,000 people killed on September 11, 2001. Gavriushin has buried rocks from ground zero under these tombstone towers, far from the place Yelena died -- a place he can no longer afford to visit. And so, as the 10-year anniversary of the terrorist attacks approaches, he mourns for her here, at his own ground zero. He remembers frantically calling his daughter that day amid the terrified crowds in Brooklyn, where he was at the time: "She never answered." (AP Photo/Mindaugas Kulbis) #

Yambem Laba, the older brother of Jupiter Yambem who was killed in the 9/11 attacks, stands on a street in Imphal, in the northeastern Indian state of Manipur, on August 17, 2011. Jupiter was a banquet manager in Windows on the World restaurant atop one of the towers. Jupiter was cremated in the states and his ashes were brought back and scattered in the Himalayas in Darjeeling and some were also scattered over a lake in Manipur. Yambem said the family has had a lot of support from friends in America and friends from all over the world. (AP Photo/Bullu Raj) #

Mariah Williams, 17, was one of the students inside the classroom at Emma E. Booker Elementary school in Sarasota, Florida, with President George W. Bush on the morning of September 11, 2001 (inset photo). Williams, photographed here in that same classroom on Wednesday, Aug. 24, 2011, was reading aloud to Bush, along with classmates, when then White House Chief of Staff Andrew Card whispered into Bush's ear that a second plane had hit the World Trade Center in New York City. (AP Photo/Brian Blanco, Inset: AP Photo/Doug Mills) #

A piece of metal with an image of the U.S. flag on it, made from aluminium recovered from the site of the World Trade Center towers in the weeks after their destruction, is shown on NASA's Mars Exploration Rover Spirit in this image released by NASA on September 8, 2011. The piece served as a cable guard for the rock abrasion tool on the rover, as well as a memorial to the victims of the September 11, 2001 attacks. (Reuters/NASA/JPL-Caltech/Cornell University) #

The Pentagon 9/11 Memorial, is seen August 21, 2011, in the southwest corner of The Pentagon Building. It is a permanent outdoor memorial to the 184 men, women, and children who lost their lives as victims of the attack, killed both in the building and on American Airlines Flight 77 in the September 11, 2001 attacks. Across the memorial grounds, 184 bench-like structures, each one dedicated to a victim, are clustered in what seems like an uneven and unsettling array throughout the main grounds of the memorial. (Paul J. Richards/AFP/Getty Images) #

Flowers rest on a bench as visitors to the Pentagon Memorial in Washington, DC, tour through the memorial on September 3, 2011, days before the 10th Anniversary of the September 11, 2001. (Jim Watson/AFP/Getty Images) #

Tabitha Rogers, 8, carries flags while helping prepare for a 9/11 memorial at the Eastside Christian Church, on August 28, 2011 in Fullerton, California. About 20 volunteers were placing 3,000 flags on the front lot -- 2,900 American flags, along with flags of other countries representing those who died on 9/11. (AP Photo/Michael Goulding/The Orange County Register) #

Workers spread straw in preparation for Saturday's dedication ceremony at the permanent Flight 93 Memorial outside Shanksville, Pennsylvania, on September 8, 2011. (Reuters/Jason Cohn) #

Journalists walk past a model of the planned development for the World Trade Center site during an event to update the public on the pace of development at the site in New York, on September 7, 2011. (Reuters/Lucas Jackson) #

Blood-stained shoes worn by Linda Lopez as she evacuated from the 97th Floor of Tower 2 on September 11, 2001 are seen in this photograph before becoming a part of the National September 11 Memorial & Museum in New York August 22, 2011. Linda Lopez was at work at the Fiduciary Trust Company on the South Tower's 97th floor when the first plane crashed into North Tower, sending a fireball past their window and radiating a heat that she said felt like being sunburned. There was quickly a sense of confusion: Was it a bomb? Were the rumors that it was a plane crash true? Should people in the South Tower ignore the advice coming over the public address system to stay put and evacuate instead? Lopez felt she had to get out. She had reached only as far as the 61st when she was thrown against a wall as the second plane crashed into the floors above her. Taking off her shoes, she continued to head down the stairs, passing firefighters heading in the opposite direction. She ran barefoot out of the building, across broken glass and other debris. "Lady, your feet are bleeding," someone said to her as she paused a few blocks away in relative safety. She put her shoes back on, and began learning the details of what it was she had just escaped from. The museum, which occupies seven stories below the ground of the World Trade Center site, is still being built at the site of the fallen towers. It is due only to open in 2012, on the 11th anniversary of the attacks. (Reuters/Lucas Jackson) #

A recovered FDNY Squad 252 helmet belonging to deceased FDNY member Kevin M. Prior is seen in this photograph before becoming a part of the National September 11 Memorial & Museum in New York August 22, 2011. Prior, a firefighter with Brooklyn's Squad 252, can be seen in video footage of the North Tower lobby recorded after the first plane hit getting ready to go upstairs. Responding to a mayday call sent out by fellow firefighters encountering breathing problems, he and five other members of the squad are thought to have been on a floor in the 20s when the tower collapsed. Prior's body was found three weeks after the attacks and was buried on Long Island, but his mother was troubled that his helmet had not been returned to the family, and said as much in a television interview. An employee at the city's Office of the Chief Medical Examiner happened to catch the broadcast, recognized Prior's squad and badge numbers, and hand-delivered the badly damaged helmet to his grateful family. (Reuters/Lucas Jackson) #

Cellphones and communication devices found in the rubble from the September 11, 2001 attacks on the World Trade Center are displayed as part of a new exhibit marking the 10th anniversary of the attacks, at the Newseum in Washington, DC, as seen August 31, 2011. The exhibit, "War on Terror: The FBI's New Focus," illustrates the story of the FBI's changing mission after 9/11 and features more than 60 artifacts including from the first World Trade Center bombing in 1993, pieces of the engines and landing gear of United Airlines Flight 175, which hit the South Tower of the World Trade Center, to the shoes used by Richard Reid in his failed airplane shoe bombing attack. (Saul Loeb/AFP/Getty Images) #

The face of a first responder is seen in artist Eric Blome's September 11 tribute sculpture on August 31, 2011, in Crystal Lake, Illinois. Blome's 22-foot-tall 2 ton sculpture incorporates four, twisted, 8 foot beams from the World Trade Center into the piece, which is adorned with sculptures that capture the emotion of the day and remember the people involved. The sculpture was commissioned by the city of Oak Lawn for its 9-11 memorial. (AP Photo/The Daily Herald, Brian Hill) #

Chase Molenaar, 14, of Yorba Linda, California, touches a piece of steel from the World Trade Center during a 10th Anniversary Remembrance of 9/11 display at the Richard Nixon Presidential Library in Yorba Linda, California, on September 5, 2011. (AP Photo/Jason Redmond) #

A woman looks through a viewing window of the World Trade Center site in New York, on August 11, 2011. This image was taken with a Holga lens mounted on a DSLR camera. (Reuters/Shannon Stapleton) #

A woman is seen reflected walking by the Teardrop memorial, a 100-foot sculpture honoring the victims of the September 11th attacks, in Bayonne, New Jersey, on August 11, 2011. This image was taken with a Holga lens mounted on a DSLR camera. (Reuters/Shannon Stapleton) #

Lighting Designer Frank Hollenkamp uses his iPad to shoot video of the Tribute in Lights ahead of the tenth anniversary of the September 11 terrorist attacks on September 7, 2011 in New York City. The Tribute in Light is comprised of 88 1-degree beams of 7000 watt searchlights focused into the sky near the site of the World Trade Center in remembrance of the September 11 attacks. (Andreas Gebhard/Getty Images) #

The Empire State Building, center, and One World Trade Center, right, rise above the Manhattan skyline in this aerial photo, on August 30, 2011 in New York. (AP Photo/Mark Lennihan) #

A welder works below ground level as work continues on the National September 11 Memorial and Museum at the World Trade Center site in New York, on July 28, 2011. (Reuters/Mike Segar) #

One World Trade Center has reached the 80th floor in this aerial photo, on August 30, 2011 in New York City. (AP Photo/Mark Lennihan) #

A view of the World Trade Center North Tower memorial pool at the National September 11 Memorial and Museum in New York, on September 6, 2011. (AP Photo/Susan Walsh) #