On September 11, 2001, four American commercial jetliners were hijacked by 19 terrorists (mostly Saudis). One plane rammed the North Tower of the World Trade Center, one plane rammed the South Tower, one plane dove into the Pentagon, and one plane (thought to be headed for Camp David) crash landed in Somerset County, Pennsylvania after the passengers revolted. Tragic and senseless as the violence and destruction on 9/11 was, it—like every event—was a consequence of something.