NEW YORK - SEPTEMBER 11:  Hijacked United Airlines Flight 175 from Boston crashes into the south tower of the World Trade Center and explodes at 9:03 a.m. on September 11, 2001 in New York City.  The crash of two airliners hijacked by terrorists loyal to al Qaeda leader Osama bin Laden and subsequent collapse of the twin towers killed some 2,800 people. (Photo by Spencer Platt/Getty Images)