The photos are from an archive of 2,779 images, and were taken by NYPD aviation unit Det. Greg Semendinger, who was ordered aloft right after the first hijacked plane struck the north tower to search for possible survivors on the rooftop.
The 13 photos were among thousands of pictures that ABC News sought under the Freedom of Information Act from the National Institute of Standards and Technology, which investigated the terrorist strike, agency spokeswoman Gale Porter said.
The 9/11 attacks killed 2,973 people and sparked a war on terror still being waged. Some 2,752 were killed in the Twin Towers, including those on the planes that ploughed into them.