The main objective of the present study is to perform an exergy analysis of a turbofan kerosene-fired engine with afterburner (AB) at sea level and an altitude of 11 000 m. The main components of this engine include a fan, a compressor, a combustion chamber, a turbine, an AB and an exhaust. Exergy destructions in each of the engine components are determined, while exergy efficiency values for both altitudes are calculated. The AB unit is found to have the highest exergy destruction with 48.1% of the whole engine at the sea level, followed by the exhaust, the combustion chamber and the turbine amounting to 29.7, 17.2 and 2.5%, respectively. The corresponding exergy efficiency values for the four components on the product/fuel basis are obtained to be 59.9, 65.6, 66.7 and 88.5%, while those for the whole engine at the sea level and an altitude of 11 000 m are calculated to be 66.1 and 54.2%. Copyright © 2007 John Wiley & Sons, Ltd.