Industrial nitric acid production uses the Ostwald process.  The combined Ostwald and Haber processes are extremely efficient, requiring only air and natural gas feedstocks.  
The Ostwald process' technical innovation is the proper conditions under which anhydrous ammonia burns to nitric oxide (NO) instead of dinitrogen ().  The nitric oxide is then oxidized, often with atmospheric oxygen, to nitrogen dioxide ():
The dioxide then disproportionates in water to nitric acid and the nitric oxide feedstock:
The net reaction is maximal oxidation of ammonia:
Dissolved nitrogen oxides are either stripped (in the case of white fuming nitric acid) or remain in solution to form red fuming nitric acid. 
Commercial grade nitric acid solutions are usually between 52% and 68% nitric acid by mass, the maximum distillable concentration. Further dehydration to 98% can be achieved with concentrated sulfuric acid|.  Historically, higher acid concentrations were also produced by dissolving additional nitrogen dioxide in the acid, but the last plant in the United States ceased using that process in 2012.  
More recently, electrochemical means have been developed to produce anhydrous acid from concentrated nitric acid feedstock.