This graphic shows the flight path of the hijacked flights out of Boston, Newark and Dulles airports that were used in terrorist attacks against the World Trade Center and the Pentagon on September 11, 2001. (Michael Sales/Reuters Graphic)

This satellite image of Manhattan, New York was collected at 11:43 a.m. EDT on September 12, 2001 by Space Imaging's IKONOS satellite. The image shows an area of white dust and smoke at the location where the 1,350-foot towers of the World Trade Center once stood. IKONOS travels 423 miles above the Earth's surface at a speed of 17,500 miles per hour. REUTERS/spaceimaging.com/HO MANDATORY PHOTO CREDIT spaceimaging.com

A huge U.S. flag flies atop the Space Needle in Seattle, Washington on September 12, 2001, the day after the World Trade Center in New York City and the Pentagon in Washington, D.C. were attacked by terrorists. Americans across the country are rallying national support as rescue and recovery efforts continue in the aftermath of the attacks. Thousands evacuated the 76-floor Bank of America Tower (right/background) on September 11 for fear of possible terrorist attacks on this building which is the tallest in the U.S. Pacific Northwest. The Space Needle has also been a suspected terrorist target in the past. REUTERS/Anthony P. Bolante

TIME magazine is publishing a special memorial edition September 13, 2001 in regards to the terrorist attacks according to managing editor James Kelly. A photograph taken by Lyle Owerka/Gamma shows the World Trade Center engulfed in flames after a hijacked airliner crashed into the building September 11. For the first time since TIME began publishing in 1927, the magazine has a black border instead of the trademark red border. REUTERS/TIME Handou

Flowers and messages scrawled in debris cover the ladder truck of Ladder Company 24 in New York Wednesday, Sept. 12, 2001, a day after the suspected terrorist attack on the World Trade Center. Ladder Company 24 lost 7 firemen in the attack, including Fire Chaplain Father Mychal Judge. (AP Photo/Amy Sancetta)

Messages scrawled in debris dust on the ladder truck door of Ladder Company 24 join a growing memorial on Wednesday, Sept. 12, 2001 in New York City to the firefighers from the company who lost their lives in the suspected terrorist attack on the World Trade Center. Ladder Company 24 lost 7 firemen in the attack, including Fire Chaplain Father Mychal Judge. (AP Photo/Amy Sancetta)

Emergency personnel and vehicles are deployed at the site of the World Trade Center in New York, Wednesday, Sept. 12, 2001. Rescue workers dug for bodies in mountains of rubble as the city struggled to recover from an airborne attack on the World Trade Center Tuesday that shut down the nation's financial capital and created a new skyline etched in terror. (AP Photo/Lawrence Jackson)

 
Emergency personnel work in the debris of the World Trade Center in New York, Wednesday, Sept. 12, 2001. Rescue workers dug for bodies in mountains of rubble as the city struggled to recover from an airborne attack on the World Trade Center Tuesday that shut down the nation's financial capital and created a new skyline etched in terror. (AP Photo/Lawrence Jackson)

A New York City fire department aerial ladder sprays water on the still smoldering wreckage of the World Trade Center in New York September 12, 2001. Two hijacked commercial airliners were deliberately crashed into the twin towers bringing them crashing to the ground September 11. REUTERS/Jim Bourg

New York Firefighter John Cleary wipes the soot from his face while taking a break from rescue work at the World Trade Center in New York on September 12, 2001. Clearly helped in the rescue of two trapped Port Authority workers, pulling the first from the rubble at one this morning and helping the second to safety at about four hours later. Commerical planes crashed into each of the twin towers towers September 11 causing them to collapse. REUTERS/Brad Rickerby