During the Sept. 11 terrorist attacks, live audio was recorded at 9:37 a.m. from air traffic controllers and 911 first responders as American Airlines Flight 77 struck the Pentagon. It is now the soundtrack for this intense revisit to that fateful day. Follow Flight 77 as it veers off course, tracked by ATC toward its deadly collision with the Pentagon. Listen and watch as 911 first responders race to the scene. It's a moment in American history that will never be forgotten.