The Air Traffic Control (ATC) productivity benefits attributed to the Corridor Integrated Weather System (CIWS) were assessed using real-time observations of CIWS product usage during three multi-day thunderstorm events in 2005 at eight U.S. Air Route Traffic Control Centers (ARTCCs). CIWS improved ATC productivity by: reducing the time required to develop, coordinate, and implement weather impact mitigation plans; increasing the number of safety and capacity-enhancing plans that were executed (e.g., more efficient, proactive rerouting and greater ability to keep routes open; [and] assisting with FAA staffing decisions. Time savings per consecutive weather day for Traffic Management Coordinators (TMCs) in an ARTCC typically were 20-95 minutes. The overall frequency of capacity-enhancing decisions increased by 177% relative to the CIWS benefits study conducted in 2003. The annual CIWS delay savings are in excess of 92,000 hours. Corresponding airline direct operations cost (DOC) savings exceeded $94M and passenger value of time (PVT) savings exceeded $201M. Annual jet fuel savings exceeded 11M gallons. The ability of the Cleveland ARTCC to develop and execute weather impact mitigation plans improved significantly (e.g., by 50-80%) when CIWS products were available to Area Supervisors as well as to the TMCs.