Flames, debris and smoke burst from the south tower of the World Trade Center as it is struck by United Airlines Flight 175 on Sept. 11, 2001. Although the south tower was the second to be struck, it would be the first to collapse.
25 Most Powerful Photos: Hijacked United Airlines Flight 175 flies toward The World Trade Center Towers shortly before slamming into the South Tower(left) ..as the North Towers burns following an earlier attack by a hijacked airliner. The stunning aerial assaults on the huge commercial complex where more than 40,000 people worked on an ordinary day were part of a coordinated attack aimed at the Nation's Financial heart.
Miriam Horrocks, seated, with 6-year-old son Michael, is presented with the U.S. flag by a U.S. Marine Corps honor guard following a funeral Mass on Sept. 17 in Media, Pa., for her late husband. Michael Horrocks, 38, was killed when hijacked United Airlines Flight 175, which he was co-piloting, crashed into the south tower of the World Trade Center.