Answer: Washington D.C.
Explanation: On September 11 2001, 19 militants associated with the extremist group hijacked four airplanes and carried out attacks against targets in the United States. Two of the planes were flown into the twin towers of the World Trade Center in New York City and a third plane hit the Pentagon just outside Washington D.C.
The fourth plane, United Airlines Flight 93, was initially flown toward Washington D.C. but crashed into a field in Stonycreek Township, Pennsylvania, after passengers thwarted the hijackers.
The flights, bound for California, were chosen because the planes were loaded with fuel for the long transcontinental journey and soon after takeoff, they commandeered the four planes and took the controls, transforming ordinary passenger jets into guided missiles.