The World Trade Center south tower (L) burst into flames after being struck by hijacked United Airlines Flight 175 as the north tower burns following an earlier attack by a hijacked airliner in New York City September 11, 2001. 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. They destroyed one of America's most dramatic symbols of power and financial strength and left New York reeling. THIRD OF SEVEN PHOTOGRAPHS REUTERS/Sean Adair SV