The Cloud Radar System (CRS) ALOFT dataset consists of calibrated radar reflectivity, Doppler velocity, linear depolarization ratio, and normalized radar cross-section estimates collected by the Cloud Radar System (CRS) onboard the NASA ER-2 high-altitude research aircraft. These data were gathered during the Airborne Lightning Observatory for Fly’s Eye Geostationary Lightning Mapper Simulator and Terrestrial Gamma-ray Flashes (ALOFT) field campaign. ALOFT aimed to study terrestrial gamma-ray flashes (TGFs) and gamma-ray glows in thunderstorms and to validate observations from the International Space Station Lightning Imaging Sensor (ISS LIS) and the Geostationary Lightning Mapper (GLM). The CRS ALOFT dataset files are available from June 15, 2023, through July 31, 2023, in HDF-5 format.