Remembering Sept. 11: Aerial Photos of World Trade Center Aftermath

The photos that follow depict the Sept. 11, 2001, attacks and their aftermath. Some 2,800 innocent people died in the attacks, including those aboard hijacked flights American 11 and United 175. ABC News obtained these images after filing a Freedom of Information Act request in 2009 with the National Institute of Standards and Technology, which collected them as part of an investigation into the collapse of the World Trade Center. (Det. Greg Semendinger/NYC Police Aviation Unit)