The infrared radiation characteristics of a jet airplane in side-flying state are measured by a 3~5 μm medium-wave and 8~12 μm long-wave thermal imager, and the infrared radiation luminance distribution of the jet nozzle and tail flame is obtained. The results show that the mid-wave and long-wave radiation of the tail flame in this state presents a symmetrical envelope distribution, and with the increase of distance, the jet beam of the tail flame gradually diffuses, and the radiation brightness gradually decreases. Under the same circumstances, for the same case, the medium-wave band tail flame is about 3.5 times longer and 6.3 times larger than the long-wave one. The tail nozzle is the brightest part of the aircraft's radiation, with contrast ratios of 20.1 in the medium-wave radiation and 8.2 in the long-wave radiation.