The present work consists in the study of the performance improvement of an aircraft for the Aerodesign competition through the use of high-lift devices. According to the 2019 competition regulation [3], the aircraft design should prioritize vehicles with low stall speed, small wing area and high lift. In Aerodesign, aircraft fly at low speeds and have small dimensions when compared to commercial ones. Thus, they operate at low Reynolds numbers, which is a complicating factor for the project. In this condition, there is a predominance of laminar flow over the surface of the airfoils, thus facilitating the separation of the boundary layer in regions closer to the leading edge. This effect is strongly associated with the loss of lift and the increase in drag of these aircraft. The flow separation closer to the leading edge complicates the use of flaps. Therefore, the study the slat was chosen because this device causes a re-energization of the flow in regions closer to the leading edge, preventing detachment. This study used a numerical tool (MSES) for the simulation of the slat-wing group and a code in MATLAB to optimize its design. A genetic algorithm was used for the optimization. Thus, increases of up to 38 per cent were obtained in the CL without significant gains in the CD. Thus, it was possible to design an aircraft with a smaller wing area and carrying a 12.3 per cente greater payload with a 6.4 per cent lower speed. Therefore, for this competition regulation, the use of the slat increased 14 per cent in the championship flight score. In the following years, it is expected a great advance in the performance of UAVs, which aerodynamic aspect has not been much explored. Therefore, it is expected that the present work contributes to the development of UAV projects.