Marwan al-Shehhi
Marwan al-Shehhi, a native of the United Arab Emirates, took over the controls of United Airlines Flight 175, the second plane that flew into the World Trade Center. Authorities believe al-Shehhi helped formulate the Sept. 11 plot in the late 1990s in Germany, where he was almost inseparable from Mohamed Atta, the hijackers' ringleader. In 2000 he attended flight school in Florida.