During the HALO-(AC)³ campaign in March-April 2022 airborne observations were performed with the High Altitude LOng range research aircraft (HALO) covering the Fram Strait and north polar regions. The flight tracks covered open ocean areas, the marginal sea ice zone, and closed sea ice cover. Furthermore, cloud conditions were observed during air mass transformation events as marine cold air outbreaks and warm air intrusions. On HALO, thermal infrared radiance, spectrally integrated over the wavelength range from 9.6 µm to 11.5 µm in nadir direction (field of view of 2.3°), was measured by the infrared pyrometer KT19 (model KT19.85 II). The given dataset comprises brightness temperature measurements with a temporal resolution of 20 Hz, provided for 16 HALO research flights (RF) during HALO-(AC)³.