This Government Accountability Office (GAO) report addresses the request to review the Department of Defense's (DOD) three largest unmanned aircraft programs in terms of cost. Specifically, GAO assessed the Global Hawk and Predator programs' acquisition strategies and identified lessons from these two programs that can be applied to the Joint Unmanned Combat Air Systems (J-UCAS) program, the next generation of unmanned aircraft. GAO recommends that DOD (1) limit Global Hawk production until the program demonstrates an integrated system and develops a new business case to justify future investments and (2) develop a sound business case and acquisition strategy for J-UCAS and follow-on efforts to ensure cost and schedule goals are met. DOD did not concur with GAO's Global Hawk recommendations because it believes it is taking appropriate measures to manage risk.