United Airlines Flight 93 ultimately crashed at 10:03 a.m. on Sept. 11, 2001, in a rural field near Shanksville, Pennsylvania.

United Airlines Flight 93 ultimately crashed at 10:03 a.m. on Sept. 11, 2001, in a rural field near Shanksville, Pennsylvania.

While Flight 93's passengers organized their revolt, a breakdown was unfolding inside the White House and the military.