The distribution of Life Cycle Costs for a typical combat aircraft between airframe, avionics, and engine is discussed. The distribution of Life Cycle Cost for the aircraft between development, production, initial support, and operation and support is compared with the distribution for the engine. The effect of fleet size and service life upon the Life Cycle Costs are indicated. The large commitment of Life Cycle Costs early in the conceptual and feasibility phase of the program is indicated. The relative effect of the choice of single or twin engine installation, of a de-rated engine or the use of an existing engine upon the engine Life Cycle Costs and the interaction with aircraft costs is discussed. The severe operating conditions for the engine of a combat aircraft are reviewed.