This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) Smoke rises into the sky following the collapse of World Trade Center Towers Tuesday, Sept. 11, 2001 in New York. (Below) The skyscraper known as One World Trade Center, right, rises in lower Manhattan, Aug. 10, 2011 in New York. (AP Photo/ Suzanne Plunkett (Top), Mark Lennihan (Bottom))

This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) People covered in dust walk over debris near the World Trade Center in New York. (Bottom) Pedestrians walk near the World Trade Center in lower Manhattan, Aug. 8, 2011 in New York. (AP Photo/ Gulnara Samilova (Top), Mark Lennihan (Bottom))

This combo image shows two documentations before and after the September 11, 2001, terrorist attack in New York City. (Top) Daniel Goodwin ("Spider Man") climbs the sheer face of the North Tower of the World Trade Center, right, in New York on May 30, 1983. (Below) Smoke pours out of the World Trade Center after an airplane struck the buildings on Tuesday, Sept. 11, 2001. (AP Photo/Suzanne Vlamis (Top), Gulnara Samoilova (Bottom))

This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) Emergency workers at ground zero on Sept. 11, 2001 after the terrorist attacks on the World Trade Center in New York City. (Bottom) Pedestrians walk along Church Street past Century 21 clothing store in lower Manhattan, Aug. 4, 2011, in New York. (AP Photos/Mark Lennihan)

This combo image shows two documentations before and after the September 11, 2001, terrorist attack in New York City. (Top) This general view shows the World Trade Center twin towers during their construction in New York on June 13, 1970. (Bottom) This photo taken Sept. 11, 2001 by the New York City Police Department shows smoke and ash engulfing the area around the World Trade Center in New York. (AP Photo/Marty Lederhandler (Top), Greg Semendinger (Bottom))

This combo image shows two documentations before and after the September 11, 2001, terrorist attack in New York City. (Top) New York's Empire State Building is illuminated at sunset in the colors of the British flag in honor of Princess Diana Thursday, Sept. 4, 1997. (Below) Smoke from the burning towers of the World Trade Center is blown east behind the Empire State Building on Sept. 11, 2001, following the terrorist attacks. (AP Photo/Michael Schmelling (Top), Marty Lederhandler (Bottom))

This combo image shows two documentations before and after the September 11, 2001, terrorist attack in New York City. (Top) New Yorkers walk over the Brooklyn Bridge on their way to work on April 7, 1980, during the transit strike. (Bottom) People flee the scene of the attacks on the World Trade center on September 11, 2001. (AP Photo/Carlos Rene Perez (Top), Mark Lennihan (Bottom))

This combo image shows two documentations before and after of the September 11, 2001, terrorist attack in New York City. (Top) The Brooklyn Bridge is seen spanning New York's East River, with the twin towers of the World Trade Center in the background, June 12, 1990. (Bottom) Smoke rising behind the Brooklyn Bridge over the East River frames the skyline of Manhattan, minus the World Trade towers, as seen from Brooklyn early Wednesday, Sept. 12, 2001, the day after hijacked airplanes crashed into both buildings causing their collapse. (AP Photo/Marty Lederhandler (Top), Kathy Willens (Bottom))

This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) Broadway near ground zero on the evening of September 11, 2001 after the September 11 terrorist attacks on the World Trade Center in New York City. (Bottom) Pedestrians pass a McDonald's restaurant on Broadway in lower Manhattan, Aug. 4, 2011, in New York. (AP Photos/Mark Lennihan)

This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) A destroyed subway station near ground zero on the evening of Sept. 12, 2001 after the September 11 terrorist attacks on the World Trade Center in New York City. (Bottom) Pedestrians walk along Church Street in lower Manhattan, Aug. 4, 2011 in New York. Behind them is the tower known as Four World Trade Center. (AP Photo/ Mark Lennihan)

This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) Pedestrians flee the area of the World Trade Center as the center's south tower collapses following a terrorist attack on the New York landmark Tuesday, Sept. 11, 2001. (Bottom) Pedestrians cross Park Row in lower Manhattan, Aug. 4, 2011 in New York. (AP Photos/Mark Lennihan)

This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) Medical and emergency workers, who are standing in front of the Millenium Hilton, look towards where the World Trade Center towers used to be, after a terrorist attack on the twin towers of lower Manhattan Tuesday, Sept. 11, 2001. (Bottom) Pedestrians pass the Hilton Hotel on Church St. in lower Manhattan, Aug. 4, 2011, in New York. (AP Photos/Mark Lennihan)

This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) Firefighters work beneath the destroyed mullions, the vertical struts which once faced the soaring outer walls of the World Trade Center towers, after a terrorist attack on the twin towers of lower Manhattan Tuesday, Sept. 11, 2001. (Bottom) The tower known as Four World Trade Center is under construction in lower Manhattan, Aug. 4, 2011 in New York. (AP Photo/Mark Lennihan)

This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) The World Trade Center destruction is shown in the aftermath of the Sept. 11 attacks in New York on Sept. 30, 2001. (Bottom) The tower known as Four World Trade Center is under construction in lower Manhattan, Aug. 9, 2011 in New York. (AP Photos/Mark Lennihan)

This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) Pedestrians flee the area of the World Trade Center as the center's south tower collapses following a terrorist attack on the New York landmark Tuesday, Sept. 11, 2001. (Bottom) The skyscraper known as One World Trade Center, center, is under construction in lower Manhattan, Aug. 4, 2011 in New York. (AP Photos/Mark Lennihan)

This combo image shows two documentations of the September 11, 2001, terrorist attack in New York City and the current day location. (Top) The south tower starts to collapse as smoke billows from both buildings of the World Trade Center in New York. (Bottom) The skyscraper known as One World Trade Center rises in the lower Manhattan skyline, Aug. 4, 2011 in New York. (AP Photo/Jim Collins (Top), Mark Lennihan (Bottom))

This combo image shows two documentations before and after the September 11, 2001, terrorist attack in New York City. (Top) The Statue of Liberty and the New York skyline frame warships and smaller craft for Operation Sail in this aerial view on July 3, 1976. (Bottom) Thick smoke billows into the sky from the area behind the Statue of Liberty, left, where the World Trade Center towers stood, Tuesday, Sept. 11, 2001. (AP Photo/ETA (Top), Daniel Hulshizer (Bottom))