In this paper, exergy, sustainability, unsustainability, environmental, enviroeconomic, ecological and inefficiency assessments are done for the JP-8-fueled turbojet engine which is designed for unmanned aerial vehicles (UAVs). It is found that the combustion chamber of the turbojet engine has the minimum exergetic efficiency (12.74%) among the components, so its improvement potential is higher than other components. The gas turbine is the most sustainable component, and the combustion chamber has higher unsustainability index rate than other components. Among the components, the highest entropy generation rate is found for the combustion chamber (179.014 kW K-1) and the lowest rate is determined for the gas turbine (0.344 kW K-1). According to environmental assessment, the turbojet engine releases 22,896.38 kg carbon dioxide emission by working 10 h in a day. According to enviroeconomic assessment, the cost of the released carbon dioxide is 3319.94$ for the daily flight. According to ecological assessment, 74.5% of the fuel exergy in the combustion chamber component is not used properly.