Plumes of smoke pour from the World Trade Center buildings in New York Tuesday, Sept. 11, 2001. Planes crashed into the upper floors of both World Trade Center towers minutes apart Tuesday in a horrific scene of explosions and fires that lead to the collapse of the 110-story buildings. The Empire State building is seen in the foreground. (AP Photo/Patrick Sison) A helicopter flies over the Pentagon in Washington, Tuesday, Sept. 11, 2001 as smoke billows over the building. The Pentagon took a direct, devastating hit from an aircraft and the enduring symbols of American power were evacuated as an apparent terrorist attack quickly spread fear and chaos in the nation's capital. (AP Photo/Heesoon Yim) Smoke billows from the towers of the World Trade Center in New York, Tuesday, Sept. 11, 2001. In one of the most horrifying attacks ever against the United States, terrorists crashed two airliners into the World Trade Center in a deadly series of blows that brought down the twin 110-story towers. (AP Photo/Jim Collins) Plumes of smoke pour from the World Trade Center buildings in New York Tuesday, Sept. 11, 2001. Planes crashed into the upper floors of both World Trade Center towers minutes apart Tuesday in a horrific scene of explosions and fires that left gaping holes in the 110-story buildings. (AP Photo/Patrick Sison) A helicopter flies over the burning Pentagon Tuesday, Sept. 11, 2001. The Washington Monument can be seen at right, through the smoke. The White House roof is visible in the trees of Washington at left. (AP Photo/Tom Horan) A man coated with ash and debris from the collapse of the World Trade Center south tower coughs near City Hall in lower Manhattan Sept. 11, 2001. (AP Photo/Amy Sancetta) The south tower collapses as smoke billows from both towers of the World Trade Center, in New York, Tuesday, Sept. 11, 2001. In one of the most horrifying attacks ever against the United States, terrorists crashed two airliners into the World Trade Center in a deadly series of blows that brought down the twin 110-story towers. (AP Photo/Jim Collins) Thick smoke billows into the sky from the area behind the Statue of Liberty where the World Trade Center towers stood Tuesday, Sept. 11, 2001. The towers collapsed after terrorists crashed two planes into them Tuesday. (AP Photo/Daniel Hulshizer) THIRD OF A SERIES OF FOUR PHOTOS--Smoke billows from one of the towers of the World Trade Center and flames and debris explode from the second tower, Tuesday, Sept. 11, 2001. In one of the most horrifying attacks ever against the United States, terrorists crashed two airliners into the World Trade Center in a deadly series of blows that brought down the twin 110-story towers. (AP Photo/Chao Soi Cheong) As seen from the New Jersey Turnpike near Kearny, N.J., smoke billows from the twin towers of the World Trade Center in New York after airplanes crashed into both towers Tuesday, Sept.11, 2001. (AP Photo/Gene Boyars) Women wearing dust masks flee across the Brooklyn Bridge from Manhattan to Brooklyn following the collapse of both World Trade Center towers Tuesday, Sept. 11, 2001 in New York. The towers previously loomed tall in the skyline behind. (AP Photo/Mark Lennihan) Police officers and civilians run away from New York's World Trade Center after an additional explosion rocked the buildings Tuesday morning, Sept. 11, 2001. In unprecedented show of terrorist horror, the 110-story World Trade Center towers collapsed in a shower of rubble and dust Tuesday morning after two hijacked airliners carrying scores of passengers slammed into the sides of the twin symbols of American capitalism. (AP Photo/Louis Lanzano) A plane approaches New York's World Trade Center moments before it struck the tower at left, as seen from downtown Brooklyn, Tuesday, Sept. 11, 2001. In an unprecedented show of terrorist horror, the 110 story towers collapsed in a shower of rubble and dust after 2 hijacked airliners carrying scores of passengers slammed into them. (AP Photo/ William Kratzke) A jet crashes into the World Trade Center in New York, Tuesday, Sept. 11, 2001. Terrorists crashed two planes into the World Trade Center, and the twin 110-story towers collapsed Tuesday morning. (AP Photo/Moshe Bursuker) Deputy U.S. marshal Dominic Guadagnoli helps a women after she was injured in the terrorist attack on the World Trade Center in New York, Tuesday, Sept. 11, 2001. (AP Photo/Gulnara Samoilova) Flames and smoke pour from a building at the Pentagon Tuesday, Sept. 11, 2001, after a direct, devasting hit from an aircraft. (AP Photo/Mandatory Credit, Will Morris) Fire and smoke billows from the north tower of New York's World Trade Center Tuesday Sept. 11, 2001 after terrorists crashed two hijacked airliners into the World Trade Center and brought down the twin 110-story towers. (AP Photo/David Karp) People flee lower Manhattan across the Brooklyn Bridge in New York, Tuesday, Sept. 11, 2001, following a terrorist attack on the World Trade Center. (AP Photo/Daniel Shanken) MANDATORY CREDIT EDITORS: NOTE GRAPHIC CONTENT--- A person falls headfirst from the north tower of New York's World Trade Center Tuesday, Sept. 11, 2001. (AP Photo/Richard Drew) Firefighters make their way through the rubble after two airliners crashed into the World Trade Center in New York bringing down the landmark buildings Tuesday, Sept. 11, 2001. (AP Photo/Shawn Baldwin) President Bush's Chief of Staff Andy Card whispers into the ear of the President to give him word of the plane crashes into the World Trade Center, during a visit to the Emma E. Booker Elementary School in Sarasota, Fla., Tuesday, Sept. 11, 2001. (AP Photo/Doug Mills) People run from the collapse of World Trade Center towers in New York, Tuesday, Sept. 11, 2001 after terrorists crashed two hijacked airliners into the World Trade Center and brought down the twin 110-story towers. (AP Photo/Suzanne Plunkett) Smoke billows from the twin towers of the World Trade Center in New York Tuesday Sept. 11, 2001. In one of the most horrifying attacks ever against the United States, terrorists crashed two airliners into the World Trade Center in a deadly series of blows that brought down the twin 110-story towers. (AP Photo/Gulnara Samoilova) The south tower of New York's World Trade Center collapses Tuesday Sept. 11, 2001. In one of the most horrifying attacks ever against the United States, terrorists crashed two airliners into the World Trade Center in a deadly series of blows that brought down the twin 110-story towers. (AP Photo/Richard Drew) Remains of the facade of Two World Trade Center is all that stands after Tuesday's terrorist attack Wednesday, Sept. 12, 2001 in New York. (AP Photo/Nick Fanelli) A military helicopter takes off after dropping off personnel at the Pentagon, Wednesday, Sept. 12, 2001, as work continued at the Pentagon after a terrorist crashed a hijacked airliner into the building Tuesday. (AP Photo/Ron Edmonds) Workers gather Wednesday, Sept. 12, 2001, to continue work at the site of the attack on the World Trade Center in New York. A large piece of the facade fallen from the one of the twin towers is in the background. (AP Photo/Amy Sancetta) Firefighters rest as rescue efforts continue at the World Trade Center in New York Wednesday Sept. 12, 2001. Many firemen are missing and feared dead in the rubble from the terrorist attack Tuesday. (AP Photo/ Beth Keiser) Firefighters unfurl an American flag from the roof of the Pentagon Wednesday, Sept. 12, 2001, as President Bush visits the area of the Pentagon where an airliner, hijacked by terrorists, crashed into the building on Tuesday. (AP Photo/Ron Edmonds) Military and fire personnel get set to unfurl a large American flag on the roof of the Pentagon, Wednesday, Sept. 12, 2001. A hijacked airliner crashed into the structure on Tuesday. (AP Photo/Steve Helber) With the Capitol in the background, flags fly at half-staff on the Washington Monument grounds Wednesday, Sept. 12, 2001 to honor the lives lost in the terrorist attacks at the Pentagon and in New York. (AP Photo/Joe Marquette) New York Gov. George Pataki, left, New York City Mayor Rudolph Giuliani, center, and Sen. Hillary Rodham Clinton, D-N.Y., tour the site of the World Trade Center disaster, Wednesday, Sept. 12, 2001. (AP Photo/Robert F. Bukaty) A man coated with ash and debris from the collapse of the World Trade Center south tower collects himself near City Hall in lower Manhattan Sept. 11, 2001. (AP Photo/Amy Sancetta) Emergency personnel carry an orange body bag with the remains of a victim of the World Trade Center crash, Thursday, Sept. 13, 2001. Two hijacked airliners crashed into the towers of the World Trade Center on Tuesday, Sept. 11, destroying both buildings. (AP Photo/Bill Farrington) Damage to the Pentagon from Tuesday's terrorist attack is seen during a Congressional tour Thursday, Sept. 13, 2001. Searchers received a signal from the black box of the plane that crashed at the Pentagon, officials said Thursday. Search crews will not be able to retrieve the black box at the Pentagon until they are able to enter the collapsed area of the Pentagon, where the plane's fuselage rests. (AP Photo/Susan Walsh, Pool) Emergency personnel carry an orange body bag with the remains of a victim of the World Trade Center crash from the rubble, Thursday, September 13, 2001. Two hijacked airliners were crashed into the towers of the World Trade Center on Tuesday, Sept. 11, destroying both buildings. (AP Photo/Bill Farrington) As rescue efforts continue in the rubble of the World Trade Center, President Bush greets firefighters at the site during a tour of the devastation, Friday, September 14, 2001. Bush is standing on a burned fire truck. Bush toured the disaster site on foot after getting a helicopter view of the devastation. More than 4,700 people remain missing in the destruction of the World Trade Center. (AP Photo/Doug Mills) President Bush, center, former New York City Mayor Rudolph Giuliani, left, and New York Gov. George Pataki, second from left, Sen. Charles Schumer, D-N.Y., second from right, and former New York City Fire Commissioner Thomas Van Essen, right, look toward the fallen buildings during a tour of the World Trade Center, in this Sept. 14, 2001photo taken in New York. Von Essen's new book, "Strong of Heart," describes a department "in complete disarray" just after the Sept. 11 attacks on the World Trade Center, with many top officials missing and its people at the scene knowing less than a shocked world watching on television. (AP Photo/Doug Mills) A candlelight vigil and memorial continues early Saturday morning, Sept. 15, 2001 on New York's Union Square, not far from the site of Tuesday's terrorist attack against the World Trade Center. With the area surrounding the World Trade Center still sealed off, Union Square has become a gathering place for people honoring victims of the attack. (AP Photo/Mark Lennihan) Work crews lift a fire truck from the debris of the collapsed World Trade Center in Lower Manhattan on Saturday evening, Sept. 15, 2001. Hundreds of firefighters who tried to save thousands trapped in the center's two towers following a terrorist attack are missing in the rubble. (AP Photo/Charles Krupa) A makeshift altar, constructed for a worship service, overlooks the the crash site of United Airlines Flight 93, Sunday, Sept. 16, 2001, in Shanksville, Pa. The plane was hijacked and crashed during Tuesday's terrorist attacks. (AP Photo/Gene J. Puskar) A black-and-white border collie named "Cowboy," a search canine for the Federal Emergency Management Agency, yelps anxiously from the top of the pile of rubble at the World Trade Center site in New York Friday, Sept. 21, 2001. The 100 FEMA dogs certified nationally as Canine Search Specialists "have a sense of smell so keen that they pick up scents in the tightest spots, where no equipment can go," says Don Hull, a Los Angeles fire batallion chief with FEMA. (AP Photo/Alan Diaz) Father Brian Jordan, second from left, blesses, Thursday, Oct. 4, 2001, a cross of steel beams found amidst the rubble of the World Trade Center by a laborer two days after the collapse of the twin towers. The cross was from World Trade tower One, and was found in World Trade building Six and moved to its present location Wednesday. Other rescue and construction workers join Jordan for the ceremony. A protective mesh hangs on the building in the background. (AP Photo/Pool, Kathy Willens) A wall displays posters of missing people from the September 11 terrorist attacks on Sept. 21, 2001.(AP Photo/David Karp) A man jumps from the north tower of New York's World Trade Center Tuesday, Sept. 11, 2001 after terrorists crashed two hijacked airliners into the World Trade Center. (AP Photo/Richard Drew) A lone firefighter moves through piles of debris at the site of the World Trade Center in New York, Tuesday, Sept. 11, 2001. Two Planes crashed into the upper floors of the World Trade Center towers minutes apart Tuesday morning, collapsing both 110-story buildings. (AP Photo/Graham Morrison)