The 28th Operations Support Squadron air traffic control tower stands tall in front of the Black Hills during the Phase II portion of an operational readiness exercise at Ellsworth Air Force Base, S.D., July 11, 2013. Air traffic controllers are responsible for guiding aircraft safely to the ground and ensure the runway is always clear of obstructions. (U.S. Air Force photo by Airman 1st Class Alystria Maurer/Released)