Abstract : Aerial refueling allows U.S. military aircraft to fly further, stay airborne longer, and carry more weapons, equipment, and supplies. Yet the mainstay of U.S. tanker forces the KC-135 Stratotanker is over 50 years old. It is increasingly costly to support and its age-related problems could potentially ground the fleet. As a result, the Air Force has initiated the $52 billion KC-46 program to replace the aerial refueling fleet. The program plans to produce 18 tankers by 2017 and 179 aircraft by 2027. The National Defense Authorization Act for Fiscal Year 2012 requires GAO to annually review the KC-46 program through 2017. This report addresses (1) progress made in 2012 toward cost, schedule, and performance goals, (2) identified program challenges, and (3) program risk mitigation tools. To address these areas, GAO reviewed key program documents, discussed development plans and results with officials from the KC-46 program office, other defense offices, and the prime contractor, Boeing. GAO assessed the program s development schedule and technology risks. GAO also assessed the program s acquisition plan to determine compliance with acquisition legislation and acquisition best practices. GAO recommends that the Department of Defense (DOD) analyze the root causes for the rapid allocation of management reserves and improve the KC-46 master schedule. DOD fully concurred with these recommendations.