Despite the improvements in engine technology, the combustion processes and wear occurred in engine components affect performance adversely. The turbine and compressor fouling, degradation mechanisms such as erosion, corrosion and mechanical clearances depending on time and thermal expansion may occur. The engine output performance and the operational efficiency of each component are affected directly by these negative cases. In this study, effects of power losses, defined by degradation mechanisms which were encountered during the compressor and turbine life cycles, on system performance were handled. Energy and exergy analysis of the loss effects in each component, defined taking into consideration the periodical component replacements, were evaluated separately. At the end of the study, the loss effects dependent on fuel consumption of turbofan engine taken as reference during the flight period were also evaluated. (C) 2017 Published by Elsevier Ltd.