The endothermic reaction of associative ionization of nitrogen and oxygen atoms was studied in the case of slow atom collisions in the framework of multichannel quantum defect theory. The diabatic potential energy curves of the NO molecule excited states were calculated using multireference configuration interaction methods implemented in MOLPRO package. It was shown that cross section dependence on the energy of the colliding atoms is in a good agreement with the experiment. The rate coefficient of the reaction was defined at the temperature 100K≤T≤1000K range. The obtained data may be used for calculating the tiered kinetics of highly excited Rydberg state population in low-temperature plasma.