Acquisition program managers are required to develop budget projections in terms of then-year dollars. That means they must adjust their future costs for escalating prices. Following a reasonable interpretation of guidance from the Department of Defense Comptroller, program managers have sometimes estimated these costs using a measure of economy-wide inflation, the Gross Domestic Product deflator. But price escalation for a particular kind of defense system may be systematically higher or lower than overall inflation. We used a hedonic cost-estimation approach to develop a price escalation index for fighter aircraft. Applying this index can vastly improve the development of budget requirements compared to using estimates of general inflation.