Watch: Second moment of silence in NYC at 9:03 a.m. when hijackers rammed plane into WTC South Tower

Hijackers crashed United Airlines Flight 175 into the South Tower of the World Trade Center at 9:03 a.m. ET on Sept. 11, 2001. The second moment of silence is one of seven to commemorate the events 25 years ago that changed the U.S. forever.

Hijackers crashed United Airlines Flight 175 into the South Tower of the World Trade Center at 9:03 a.m. ET on Sept. 11, 2001. The second moment of silence is one of seven to commemorate the events 25 years ago that changed the U.S. forever.