Among the most important problems currently faced by air transport, we can distinguish the adverse impact of aircrafts on the natu-ral environment, as well as the rising costs of transport. One of the possibilities to improve this situation is better adjustment of aircraft characteristics to the performed transport tasks, taking into account all the requirements and limitations that exist in air traffic and the adverse impact of air transport on the natural environment. It is reflected in the research tasks conducted under the SESAR program. The aspiration to minimize the adverse impact of aircrafts on the environment is executed, among others, through determining such trajectories that are characterized by minimal fuel consumption or minimal emission of harmful substances in the engines exhausts. These goals are corresponding with the research conducted and described in the paper. The main aim of the work was to analyse the impact of wind speed and direction on the emission of harmful substances of a jet aircraft performing a flight on a given route. For research purposes, the route between two Polish cities Gdansk and Rzeszow was considered. The distance between the two airports was divided into sections for which wind direction and strength were determined (read from the windy.com website). Next, the aircraft per-formance was determined and the fuel consumption and the amount of harmful compounds (CO2, NOx, CO and HC), emitted in the en-gines exhausts were determined for the route from Gdansk to Rzeszow (under favourable wind conditions) and on the return route – from Rzeszow to Gdansk (under unfavourable wind conditions). For comparative purposes, emission of these substances for windless condi-tions was also determined. The results are presented in tables and depicted in the graph, as well as discussed in the conclusions of the paper.