The U.S. Air Force has long struggled to incorporate new weapon system logistics requirements and support system design considerations into its broader sustainment enterprise early in the acquisition process. To help inform Air Force decisionmaking with regard to sustainment sourcing, RAND Project AIR FORCE researchers explored and adapted lessons from the transaction cost accounting literature. The result is a powerful economic-based framework that has three primary benefits when it comes to addressing sustainment planning challenges: It is a repeatable, analytically driven decision tool that does not require large amounts of data; it considers repair source decisionmaking in the context of the broader Air Force enterprise; and it is potentially applicable to other aspects of sustainment planning, such as managing government-mandated repair sourcing mixes and informing other Air Force sustainment community responsibilities. This report demonstrates how the framework can be used to select among depot maintenance strategies by applying it to the F-35 Joint Strike Fighter, the largest acquisition program in U.S. Department of Defense history. Although the U.S. government will retain the capability to perform the range of depot-level repairs for the F-35, 40 percent of the workload — known as "above core" — can be considered for sourcing to an organic Air Force facility, another military service's facility, a foreign partner, or the private sector. The framework helps planners visualize program data and compare new acquisition programs with legacy Air Force systems. In this way, it offers the Air Force additional leverage in responding to technology developments and vetting contractors' engineering, reliability, and maintainability projections for new weapon systems.