The energy crisis demands that we review the cost versus performance of various alternatives to attempt to understand what can be done and in what priority the various alternatives should be addressed. This analysis addresses, on a first order basis, some of the engine alternatives suggested to reduce the impact of rising fuel prices. It is concluded, based on the analysis which considered the depreciation of investment, the cost of capital, insurance and maintenance expenses, as well as fuel savings, that in order of priority, we must: 1. Investigate the optimum way to improve current in-service engine performance at minimum increase in maintenance cost. 2. Investigate the possibility of improving current engines by means of modification within current dimensions to improve components. Only after these are investigated and fuel prices have substantially increased, will retrofit of new engines on old aircraft be worthy of consideration.There is need to develop the methodologies to predict accurately the total cost impact versus performance improvement for future decision making. A suggested approach and the results of such an analysis which support the priorities listed is presented.