Prior to his appointment as Center Director, Littles served as NASA Associate Administrator for the Office of Space Flight (1994-1996). Littles began his NASA career in 1967 when he worked as an engineer in Marshall's former Propulsion and Vehicle Engineering Directorate. He worked in various capacities at the Marshall Center, including Science Engineering Director (1988-1989) and Center Deputy Director (1989-1994) before transferring to NASA Headquarters in 1994, as Chief Engineer. Littles was involved in the redesign of the space shuttle booster rockets, blamed for the Challenger disaster in 1986.