This article focuses on the study of the reliability of unmanned aerial vehicles (UAVs), whose role in various sectors, including the rescue sector, is dynamically increasing. The aim of the study was to analyze the key factors affecting UAV failure rate and determine their impact on the time to failure. Statistical analysis and simulations were conducted within the study, based on collected data, to investigate the relationship between the type of failure and the system's time to failure. The results of the analyses showed that the time to failure differs significantly depending on the cause, particularly for battery-related failures. It was also found that unfavorable atmospheric conditions, such as strong wind, high temperature, and high humidity, significantly shorten the system's time to failure compared to normal conditions, with this effect being similar for different types of unfavorable weather.