In 2015, the United States and partner governments in the F-35 program began considering the use of a three-year block buy (BB) contract for procurement of F-35 aircraft during fiscal years 2018-2020. This report assesses potential cost savings available through use of a three-year block buy contract for procurement of F-35 aircraft during fiscal years 2018-2020–approximately $2.1 billion, or 4.9 percent of the cost of annual contracting.