History of the United States (1991–2008) South Tower less than twenty minutes later at 9:03 A.M. (EST), resulting in the collapse of both 110 story skyscrapers, and the destruction of the World Trade Center. The third hijacked plane, American Airlines Flight 77, was crashed into the Pentagon (the headquarters of the United States Department of Defense) in Arlington County, Virginia, demolishing a section of the outer southwest facing wall. After discovering that their plane, United Airlines Flight 93, was going to be used as a missile, passengers attempted to regain control of the plane which had been redirected towards Washington, D.C. However, after regaining control from
Office of the Secretary of Defense Office of the Secretary of Defense The Office of the Secretary of Defense (OSD) is a headquarters-level staff of the United States Department of Defense. It is the principal civilian staff element of the U.S. Secretary of Defense, and it assists the Secretary in carrying out authority, direction and control of the Department of Defense in the exercise of policy development, planning, resource management, fiscal, and program evaluation responsibilities. OSD (along with the Joint Staff) is the Secretary of Defense’s support staff for managing the Department of Defense, and it corresponds to what the Executive Office of the President of