How is nitric oxide used?
In today's chemical industry, there are minimal uses of nitric oxide 'as is.' The ammonia oxidation reaction is most commonly used as the first of three sequential reaction steps that convert ammonia into ammonium nitrate, a fertilizer. In the second step, nitric oxide is reacted with more oxygen and water to form nitric acid. In the third step, nitric acid is reacted with ammonia to form ammonium nitrate. (Since ammonia is not something that you want to ship all over the place, there are upstream processes that you can use to generate the ammonia.)
Nitric acid, the result of ammonia oxidation followed by cooling and absorption / air oxidation, does have some uses 'as is.' About ten percent of all of the nitric acid made in the U.S. is not converted into ammonium nitrate. Nitric acid can be used as a reactant (in a cyclohexane-based process) to make adipic acid, which is then used as a nylon reactant. It can also be used as a reactant to nitrate toluene, either fully to trinitrotoluene (TNT) or partially to dinitrotoluenes, which are then further reacted to form toluene diisocyanate (TDI).
For more information on the uses of nitric oxide and nitric acid, please consult these references.