The IR signature and radiative base heating from an aircraft plume have been important factors for aircraft survivability in modern battle fields. In order to enhance the aircraft survivability and reduce the base heating, infrared signatures emitted from an aircraft exhaust plume should be determined. In this work, therefore, IR signatures and radiative base heating characteristics are examined in the plume exhausted from the aircraft with operating at altitude of 5 km in M=0.9 and 1.6, respectively. As a result, it is found that the particular wavelength IR signature has high spectral characteristics because of $H_2O$ and $CO_2$ gases in the plume, and the radiative heat flux coming into the base plane increases with higher Mach number and shorter distance.