CIRRUS-HL, the only HALO cloud mission combining in situ and remote sensing cloud instrumentations since 2014, uses state-of-the-art cloud probes, and novel ice residual, aerosol, trace gas and radiation instruments to investigate nucleation, life cycle and radiative impact of ice clouds in high latitudes and of anthropogenic contrail cirrus. The aircraft observations are accompanied by remote sensing from satellite and by numerical simulations with global and process-based models. The campaign is complementary linked to international polar research activities by focusing on the physics of ice clouds and anthropogenic perturbations.