Researchers at the NASA Ames Research Center have been developing decision support tools for air traffic controllers for the past fifteen years. The cornerstone of that effort is the Center-TRACON Automation System, or CTAS. CTAS is a set of software decision support tools designed to help air traffic controllers manage the increasingly complex traffic flows at large airports. The tools in CTAS benefit air traffic controllers by reducing stress and workload, and benefit air travelers by reducing delays and increasing safety. In 1998, portions of CTAS were chosen by the Federal Aviation Administration (FAA) as the fundamental building blocks of future automation and are included in the FAA's Free Flight Phase 1 implementation nationwide. In a unique design process, scientists, engineers, and air traffic controllers combined their talents to create the algorithms, software and human interfaces in CTAS, fashioning them into tools which controllers use to effectively solve complex traffic problems. Mr. Davis will provide an overview of CTAS and ongoing research and development efforts to expand the capabilities of CTAS towards free flight. Information on CTAS can be found at: http://www.ctas.arc.nasa.gov/