The contrail avoidance research team from the EUROCONTROL Maastricht Upper Area Control Centre (MUAC) outlines the key areas of research that are being undertaken to understand the climate impacts of contrails. Condensation trails, or contrails, are ice clouds that form as a result of the mixing of cold, humid air with aircraft engine exhaust plumes. They influence Earth's energy equilibrium by altering global cloudiness and interacting with both incoming solar radiation and outgoing thermal radiation. Contrails, especially at night, have been shown to result in net positive radiative forcing (RF), thereby contributing to climate change. Studies indicate that contrails and contrail cirrus may be the largest contributor to aviationattributable RF, potentially exceeding contributions of aviation carbon dioxide (CO2) emissions. (....)