NEQAIR v15.x, Nonequilibrium Radiative Transport and Spectra Program. NEQAIR has been NASAs main radiative heating code for the last 35 years. It is a line-by-line radiation code that computes spontaneous emission, absorption and stimulated emission due to transitions between various energy states of chemical species along a line-of-sight through a non-uniform gas mixture. This allows NEQAIR to calculate the radiative heat flux and detailed spectra at a specified location. NEQAIR v15.0 has focused on improving stability, solution robustness, usability and providing different options for running the code.