All 19 hijackers were al-Qaeda members, divided among the four planes. Here's a look at who they were and who else was involved in planning the attacks. | World News

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

Marking 25 years since 9/11, this photo feature revisits the attacks, timeline, and human toll that reshaped global history.