This Note describes RAND's latest study of cost estimating relationships for new military aircraft turbine engine development and production programs. It presents equations for estimating development and production costs and time of arrival for U.S. military turbojet and turbofan engines. The study derives new cost estimating relationships from an expanded database and uses new diagnostic statistics to screen the relationships and to evaluate the characteristics of the preferred set. Section II of this Note identifies the data used, explains the criteria and rationale for selecting explanatory variables, and describes recently developed regression diagnostics. Section III presents the preferred set of relationships. Comments on these results, a comparison with DAPCA equations, suggestions for the use of the cost estimating relationships, and directions for possible future research are discussed in Sec. IV. Supporting statistics for the predictive models are available in the appendix.