The paper presents the energy consumption and emissions of pollutants in the exhausts during the take-off operation mission of a Short Take-Off and Landing (STOL) aircraft equipped with a traditional and hybrid propulsion system. This research is part of the contemporary trend of research aimed at reducing the impact of aviation on the natural environment. The analyzed propulsion system consists of turbine engines and electric motors cooperating with them. In this work, on the basis of data from flight tests, the energy requirement for the aircraft to perform the intended mission was determined. On this basis, fuel consumption and the corresponding pollutant emissions were determined for an aircraft with a traditional power unit. For comparison, an aircraft with a hybrid propulsion system with the same mass as an aircraft with a traditional propulsion system was used. Then, energy consumption, fuel consumption and emission of CO2, CO, NOx, VOC, PM10 and PM2.5 were obtained for both aircraft variants. The most important results of the conducted research include a reduction in CO2 emissions by 23% and NOx emissions by 46% in the case of the hybrid propulsion. This indicates potential benefits of using hybrid propulsion in aviation.