New York City firefighters look at the detroyed facade of the World Trade Center September 13, 2001 two days after the twin towers were destroyed when hit by two hijacked passenger jets.

Chris Hondros/Getty Images

Smoke still bellows from where the World Trade Center once stood before terriorsts attacked and demolished the building in New York City, NY., Sept. 12, 2001.

Scott Gries/ImageDirect

A satellite image of lower Manhattan shows smoke and ash rising from the site of the World Trade Center at 11:43 a.m. September 12, 2001 in New York City.

spaceimaging.com/Getty Images

A truck carrying debris passes by a parking lot filled with dust as rescue workers continue salvage operations around the World Trade Center September 12, 2001, one day after both towers collapsed after a terrorist attack.

Jose Jimenez/Primera Hora/Getty Images

Smoke billows from where the World Trade Center twin towers stood September 12, 2001 in New York City.

Chris Hondros/Getty Images

The front page of the Chicago Sun-Times with a headline that reads 'OUTRAGE' regarding the terrorist attack on New York City's World Trade Center is displayed September, 12, 2001 in Chicago.

Tim Boyle/Getty Images

An American flag, erected by rescue workers, stands in the wreckage of the World Trade Center September 13, 2001 in New York City, two days after the twin towers were destroyed when two hit by two hijacked passenger jets.

Chris Hondros

New York City police officers gather at the wreckage of the World Trade Center September 13, 2001 in New York City, two days after the twin towers were destroyed when two hit by two hijacked passenger jets.

Chris Hondros

Fires still burn amidst the rubble of the World Trade Center September 13, 2001 days after the September 11, 2001 terrorist attack.

U.S. Navy Photo by Jim Watson/Getty Images

A note is taped to a window after the World Trade Center terrorist attack September 13, 2001 in New York City.

Joe Raedle/Getty Images

People walk past a sign for Morgan Stanley employees in Times Square September 13, 2001, two days after the World Trade Center terrorist attack in New York City.

Joe Raedle/Getty Images

Rescue workers sift through the wreckage of the World Trade Center September 13, 2001 in New York City, two days after the twin towers were destroyed when two hit by two hijacked passenger jets.

Chris Hondros/Getty Images

People pause at a memorial on the fire truck of Ladder Company 24 September 13, 2001 in New York City two days 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.

Jose Jimenez/Primera Hora/Getty Images

Mourners pay their respects outside the U.S. Embassy September 13, 2001 in London after two hijacked airplanes slammed into the World Trade Center in New York as part of a suspected terrorist attack on New York City and Washington DC September 11, 2001.

Anthony Harvey/Getty Images

People walk in Times Square September 13, 2001, two days after the World Trade Center terrorist attack in New York City.

Joe Raedle/Getty Images

Construction workers in Times Square put up American flags and signs September 13, 2001, two days after the World Trade Center terrorist attack in New York City.

Joe Raedle/Getty Images

A survivor is pulled from the rubble of the World Trade Center September 13, 2001 in New York City two days after two hijacked airplanes slammed into the twin towers, levelling them.

Mario Tama/Getty Images

A US flag flies from a television antenna September 13, 2001 amid the rubble of the World Trade Center after an aircraft crashed into it September 11 as part of a terrorist attack. The antenna was once at the top of one of the 110 story twin towers.

FEMA/Getty Images

A rescuer takes a break from the toil of the recovery efforts surrounded by what once was a bustling area of world commerce September 13, 2001 in New York's financial district.

Jim Watson/US Navy/Getty Images

An aerial view shows only a small portion of the crime scene September 16, 2001 where the World Trade Center collapsed following the September 11, 2001 terrorist attack in New York City. Surrounding buildings were heavily damaged by the debris and massive force of the falling twin towers. Clean-up efforts are expected to continue for months.

Eric J. TIlford/U.S. Navy/Getty Images

(FILE PHOTO) FBI agents, firefighters, rescue workers and engineers work at the Pentagon crash site on September 14, 2001, after a highjacked American Airlines flight slammed into the building on September 11. The terrorist attack caused extensive damage to the west face of the building and followed similar attacks on the twin towers of the World Trade Center in New York City.

Photo by Cedric H. Rudisill/DOD/Getty Images

An aerial view shows only a small portion of the crime scene September 16, 2001 where the World Trade Center collapsed following the September 11, 2001 terrorist attack in New York City. Surrounding buildings were heavily damaged by the debris and massive force of the falling twin towers. Clean-up efforts are expected to continue for months.

Eric J. TIlford/U.S. Navy/Getty Images

An aerial view shows only a small portion of the crime scene September 16, 2001 where the World Trade Center collapsed following the September 11, 2001 terrorist attack in New York City. Surrounding buildings were heavily damaged by the debris and massive force of the falling twin towers. Clean-up efforts are expected to continue for months.

Eric J. TIlford/U.S. Navy/Getty Images

NYPD police officer Ken Radigan rubs his eyes after briefly sleeping in a pew at St. Paul's Episcopal Chapel, near the site of the World Trade Center attack, September 21, 2001 in New York City. The chapel is serving as a relief area for rescue workers.

Photo by Mario Tama/Getty Images

NYPD police officer Ken Radigan rubs his eyes after briefly sleeping in a pew at St. Paul's Episcopal Chapel, near the site of the World Trade Center attack, September 21, 2001 in New York City. The chapel is serving as a relief area for rescue workers.

Photo by Mario Tama/Getty Images

EW YORK - SEPTEMBER 11, 2001: (SEPTEMBER 11 RETROSPECTIVE) A firefighter breaks down after the World Trade Center buildings collapsed September 11, 2001 after two hijacked airplanes slammed into the twin towers in a terrorist attack.

Mario Tama/Getty Images

NYPD police officer Ken Radigan rubs his eyes after briefly sleeping in a pew at St. Paul's Episcopal Chapel, near the site of the World Trade Center attack, September 21, 2001 in New York City. The chapel is serving as a relief area for rescue workers.

Photo by Mario Tama/Getty Images

NYPD police officer Ken Radigan rubs his eyes after briefly sleeping in a pew at St. Paul's Episcopal Chapel, near the site of the World Trade Center attack, September 21, 2001 in New York City. The chapel is serving as a relief area for rescue workers.

Photo by Mario Tama/Getty Images

An Aerial View Shows Ground Zero Of The World Trade Center Disaster Area September 21, 2001 In New York City Following The Suicide Terrorist Attacks On The Twin Towers.

A Search And Rescue Canine Team Emerge From The Pile Of Rubble September 21, 2001 At The World Trade Center Disaster Area In New York City.

FEMA

The World Trade Center collapse site in New York smolders in this photo released April 19, 2001.

FEMA

This LIDAR, Light Detection and Ranging, image of the World Trade Center collapse site in New York released April 19, 2001 shows the topography of the area. LIDAR creates the image by bouncing a laser beam off the ground and calculating the time it takes for the beam to return. The darker red areas indicate lower elevations.

NYC Office of Emergency Management/Getty Images

Different levels of destruction and building stability at the destroyed World Trade Center complex are shown in this September 19, 2001 graphic released by the New York City Office of Emergency Management.

Pool Photo/NYC Office of Emergency Management

Different levels of destruction and building stability at the destroyed World Trade Center complex are shown in this September 19, 2001 graphic released by the New York City Office of Emergency Management.

Pool Photo/NYC Office of Emergency Management

Members of the Miami-Dade, Florida Rescue Task Force work within the rubble of what used to be the World Trade Center September 20, 2001 in New York City. Federal and City officials are still calling their work a rescue and recovery effort but hopes are quickly fading for finding any survivors.

Jose Jimenez/Primera Hora Newspaper/Getty Images

Firemen look towards the rubble of what used to be the World Trade Center September 20, 2001 in New York City. Federal and City officials are still calling salvage work at the site a rescue and recovery effort but hopes are quickly fading for finding any survivors.

Jose Jimenez/Primera Hora Newspaper/Getty Images

Firefighters hose down the smoldering remains of #7 World Trade Center September 18, 2001 in New York as search and rescue operations continue at the site of last week's terrorist attack

Workers at the site of New York's World Trade Center terrorist attack pass a container September 18, 2001 that is reserved for aircraft parts. The poster at right shows searchers what the flight recorders of the two airliners that slammed into the twin towers would look like. None of the two planes'' recorders have been reported recovered.

Undated photos of suspected hijackers of American Airlines flight #11, United Airlines flight #93 , American Airlines flight #77 and United Airlines flight #175 involved in the terror attack on the United States September 11, 2001, released by the FBI September 27, 2001 in Washington, DC.

FBI/Getty Images

: A painter working on a mural in remembrance of the World Trade Center attack in the east village in New York City. 9/18/01

Scott Gries/Getty Images

The front of the New York Stock Exchange almost one week after the World Trade Center attack. 9/18/01

Scott Gries/Getty Images

New York City Mayor Rudolph Giuliani gestures before the Mets'' game against the Atlanta Braves at Shea Stadium in Flushing, NY September 21, 2001 in the first major sporting event in the New York area since the World Trade Center disaster.

Ezra Shaw/Allsport

NYPD police officer Ken Radigan rubs his eyes after briefly sleeping in a pew at St. Paul's Episcopal Chapel, near the site of the World Trade Center attack, September 21, 2001 in New York City. The chapel is serving as a relief area for rescue workers.

Photo by Mario Tama/Getty Images

A police officer tries to control crowds during an identification check September 17, 2001 in southern Manhattan, New York City as the area near the World Trade Center re-opened for business for the first time since the center was attacked by hijacked jetliners.

Spencer Platt/Getty Images

Members of the National Guard keeps watch as people walk through New York's financial district September 17, 2001 as Wall Street re-opened for business six days after a terrorist attack which levelled the World Trade Center.

Joe Raedle/Getty Images

Members of the National Guard keeps watch as people walk through New York's financial district September 17, 2001 as Wall Street re-opened for business six days after a terrorist attack which levelled the World Trade Center.

Joe Raedle/Getty Images

A New York police officer uses a mask to protect himself from dust and smoke as he patrols New York's financial district September 17, 2001 six days after a terrorist attack levelled the World Trade Center.

Joe Raedle/Getty Images

The Hospital Ship USNS Comfort docks September 17, 2001 in Manhattan. The ship was deployed to New York to render assistance following the September 11, 2001 terrorist attack on the World Trade Center.

U.S. Navy Photo by Eric J. Tilford/Getty Images

A man pauses to look at a Brooklyn, New York mural September 18, 2001 in memory of the World Trade Center and the over 5,000 people who died in the terrorist attack. The September 11 attack was the worst terrorist act in American history.

Spencer Platt/Getty Images

A woman is assisted by a National Guardsman September 17, 2001 in southern Manhattan, New York City as the area near the World Trade Center re-opened for business for the first time since the center was attacked by hijacked airliners.

Spencer Platt/Getty Images

Rescue workers form a 'bucket brigade' to comb through debries for survivors at the scene of the World Trade Center collapse September 15, 2001 in New York City.

Preston Keres/US Navy//Getty Images

A search dog sleeps behind a New York firefighter at the scene of the World Trade Center collapse September 15, 2001 in New York City.

Preston Keres/US Navy//Getty Images

A New York firefighter sits amid the debries of the World Trade Center September 15, 2001 in New York''s financial district.

Preston Keres/US Navy//Getty Images

Lower Manhattan Show Smoke Rising From The Site Of The World Trade Center Terrorist Attack September 15, 2001 In This Space Imaging's Ikonos Satellite Image. The Image Shows The Remains Of The 1,350-Foot Towers Of The World Trade Center, And The Debris And Dust That Has Settled Throughout The Area. Also Visible Are The Many Emergency And Rescue Vehicles In The Streets In The Vicinity Of The …

People gather for prayer and 3 minutes of silence ifor the victims of the World Trade Center tragedy inside St. Patrick's Cathedral on Fifth Avenue in New York City.

Photo by Dave Hogan/Mission Pictures/Getty Images

Three women look at flyers of the missing from the World Trade Center disaster at a Prayer Wall September 15, 2001 in New York four days after the bombing of the landmark New York twin towers

Spencer Platt/Getty Images

A bronze sculpture of a businessman and his briefcase sits amid heavy machinery and rubble of the destroyed World Trade Center September 15, 2001 in New ork City. What once was a representation of the financial district is now a small memorial for those who lost their lives in the September 11 terrorist attack.

Eric J. Tilford/US Navy/Getty Images

The U.S. Navy hospital ship USNS Comfort passes the Statue of Liberty September 15, 2001 enroute to Manhattan to provide assistance to victims of the September 11, 2001 terrorist attack on the World Trade Center.

U.S. Navy Photo by Jim Watson/Getty Images

Smoke rises from the site of the World Trade Center terrorist attack September 15, 2001 in New York City.

ool photo courtesy of NYC Office Of Emergency Management/Getty Images

A man writes a message during a vigil, for the victims of the attack on the World Trade Center and Pentagon, at Manhattan's Union Square Park September 14, 2001 in New York City

Joe Raedle/Getty Images

A makeshift memorial is made during a candle light vigil, for the victims of the attack on the World Trade Center and Pentagon, at Manhattan's Union Square Park September 14, 2001 in New York City.

Joe Raedle/Getty Images

US President George W. Bush looks out a window at the damaged Pentagon aboard his helicopter Marine One September 14, 2001 while en rote to New York to tour the site of the World Trade Center attack.

Eric Draper/White House/Getty Images

A firefighter rubs his eyes at the scene of the World Trade Center disaster September 14, 2001 in New York's financial district.

Jim Watson/US Navy/Getty Images

A firefighter rubs his eyes at the scene of the World Trade Center disaster September 14, 2001 in New York's financial district

Jim Watson/US Navy/Getty Images

Rescue crews gather at the destroyed World Trade Center the morning of September 14, 2001 in New York City three days after the two hijacked passenger jets slammed into the twin towers.

Spencer Platt//Getty Images

A person looks for loved ones at a missing persons board across the Saint Vincent Hospital four days after the terrorist attack at the World Trade Center September 14, 2001 in New York City.

Jose Jimenez/Primera Hora//Getty Images

New Yorkers have set up a candlelight vigil with notes and gifts to commerate the missing from the World Trade Center attack in Union Square in New York City on September 13, 2001. This artwork shows the twin towers with the message 'We are still Standing'.

Jose Jimenez/Primera Hora//Getty Images

People have been posting notices for mission people on a 'Wall of Peace' at Bellevue Hospital in New York City after the destruction of the World Trade Center by terrorists on Tuesday, September 11, 2001

Dave Hogan/Mission Pictures/Getty Images

Friends and family of missing people post signs with photos and descriptions to help locate them outside the armory on Lexington Ave in New York City on September 13, 2001 where information is being gathered for all the missing as a result of the attack on the World Trade Center

Gabe Palacio/Getty Images

Bodies are pulled from the rubble of the World Trade Center by rescue workers September 13, 2001 in New York City two days after two hijacked airplanes slammed into the twin towers, levelling them.

Dave Hogan/Mission Pictures/Getty Images

Bodies are pulled from the rubble of the World Trade Center by rescue workers September 13, 2001 in New York City two days after two hijacked airplanes slammed into the twin towers, levelling them.

Dave Hogan/Mission Pictures/Getty Images

Bodies are pulled from the rubble of the World Trade Center by rescue workers September 13, 2001 in New York City two days after two hijacked airplanes slammed into the twin towers, levelling them.

Dave Hogan/Mission Pictures/Getty Images

Rescue workers and medical personnel try to extricate a survivor from the wreckage of the World Trade Center September 13, 2001 in New York City. Rescue efforts continued two days after two airplanes slammed into the twin towers in an alleged terrorist attack, levelling them.

Mario Tama/Getty Images

Smoke rises from the wreckage of the World Trade Center September 13, 2001 in New York City. Rescue efforts continued two days after two airplanes slammed into the twin towers in an alleged terrorist attack, levelling them.

Mario Tama/Getty Images

Dennis Diaz, a member of Local 100 of the SEIU, looks over the Wall of Prayers September 13, 2001 at the entrance to Bellevue Hospital in New York City for 80 members of the union who are missing after Tuesday's deadly terrorist attack on the World Trade Center. All of the workers were employed at the Windows of the World Restaurant on the 106th floor of one of the towers.

Jose Jimenez/Primera Hora/Getty Images