Looking at pictures from the 2001 9/11 attacks on the World Trade Center remains a surreal experience. These images show the scale of the disaster through the eyes of the photographer in the police helicopter on the day.
ABC News recently obtained these images after filing a Freedom of Information Act request in 2009 with the National Institute of Standards and Technology, which had collected as part of an investigation into the collapse of the World Trade Center.
(Det. Greg Semendinger/NYC Police Aviation Unit)