The impact of contrails on Earth’s climate is probably not negligible, yet there are only a few initiatives aimed at mitigating the influence of aviation on the environment. To achieve zero CO2 emissions, aircraft manufacturers and airlines propose complex and costly methods and technologies such as synthetic fuels, hybrid engines, or expensive carbon offsetting. On the other hand, contrail mitigation by achievable operational measures has the potential to achieve benefits with a very positive cost-benefit ratio without the need for a complex technological change in aviation. It seems that one suitable tool for contrail mitigation is the change in flight level. Therefore, we focused on the assessment of flight levels with typical contrails occurrence and common flight levels used by air traffic management. Some influence of tropopause height throughout the year was presumed to be a factor, therefore we studied different times of the year. The tropopause height influences not only contrail occurrence but also the preferred flight level, as airlines tend to avoid flying directly in the tropopause. We present some basic statistics about the frequency of contrail occurrence based on flight level. We focused on long-lived contrails to emphasize the more important contrails in this context. Information about flight levels is based on ADS-B data transmitted by aircraft and recorded by a ground station near the place of contrail occurrence, which was based on optical survey.