The reaction between superthermal N(4S) atoms produced by exothermic processes and O2 has been proposed to explain observations of highly rotationally excited nitric oxide in the sunlit thermosphere. We examine the importance of this mechanism using a detailed calculation of the fast N(4S) atoms energy distribution. It is shown that the hot thermal N atoms are able to produce rotationally excited NO in the upper thermosphere through the reaction of O2 with N(4S). By contrast, near the NO peak at 110 km, the Maxwellian nitrogen atoms produce substantially less rovibrationally excited NO than the superthermal component. Consequently, the non Maxwellian N(4S) atoms show a clear spectral signature in the (1-0) and (2-1) bandheads at this altitude. The calculated rovibrationally excited NO concentration at 140 km is shown to be consistent with the value derived from the analysis of infrared airglow spectra. ¿ American Geophysical Union 1996