A school run, a doctor's visit, a budget fight in Congress. Small shifts in plans kept dozens of people out of the World Trade Center that morning.

Two of the hijacked planes struck the Twin Towers in New York and a third crashed into the Pentagon. | World News

A visual timeline of how the events unfolded in the U.S. on September 11, 2001, when terrorists hijacked planes and crashed them into key buildings, including the Twin Towers of…