A view from the Hudson River of lower Manhattan's financial district, including the World Trade Center Twin Towers in an undated photo in New York City.

(FILE PHOTO) A view of the construction of the 110th floor twin story World Trade Center Towers in an undated photo in New York City. Two hijacked planes crashed into the World Trade Center September 11, 2001, destroying the towers.

(FILE PHOTO) A view of the construction of the 110th floor twin story World Trade Center Towers in an undated photo in New York City. Two hijacked planes crashed into the World Trade Center September 11, 2001, destroying the towers.

(FILE PHOTO) A view of the construction of the 110th floor twin story World Trade Center Towers in an undated photo in New York City. Two hijacked planes crashed into the World Trade Center September 11, 2001, destroying the towers.

(FILE PHOTO) A view of the construction of the 110th floor twin story World Trade Center Towers in an undated photo in New York City. Two hijacked planes crashed into the World Trade Center September 11, 2001, destroying the towers.

(FILE PHOTO) A view of the construction of the 110th floor twin story World Trade Center Towers in an undated photo in New York City. Two hijacked planes crashed into the World Trade Center September 11, 2001, destroying the towers.

(FILE PHOTO) A view of the construction of the 110th floor twin story World Trade Center Towers in an undated photo in New York City. Two hijacked planes crashed into the World Trade Center September 11, 2001, destroying the towers.

(FILE PHOTO) A view of the construction of the 110th floor twin story World Trade Center Towers in an undated photo in New York City. Two hijacked planes crashed into the World Trade Center September 11, 2001, destroying the towers.

(FILE PHOTO) A view of the construction of the 110th floor twin story World Trade Center Towers in an undated photo in New York City. Two hijacked planes crashed into the World Trade Center September 11, 2001, destroying the towers.

NEW YORK - JUNE 30, 2000: A satellite image of lower Manhattan was taken June 30, 2000 by the IKONOS satellite over New York City. The image shows the 110-story Twin Towers.

Space Imaging/Getty Images

NEW YORK - JUNE 30, 2000: A satellite image of lower Manhattan was taken June 30, 2000 by the IKONOS satellite over New York City. The image shows the 110-story Twin Towers.

Space Imaging/Getty Images

NEW YORK - JUNE 30, 2000: A satellite image of lower Manhattan was taken June 30, 2000 by the IKONOS satellite over New York City. The image shows the 110-story Twin Towers.

Space Imaging/Getty Images

5 Sep 2001: The view of the New York skyline with the World Trade Center at sunset taken from the US Open at the UATA National Tennis Center in Flushing, New York.

Jamie Squire /Allsport