or ▁PR AS M ) ▁is ▁passenger ▁( or ▁scheduled ▁ticket ) ▁re venue ▁per ▁AS M . ▁Oper ating ▁R AS M ▁or ▁Total ▁R AS M ▁is ▁the ▁air line ' s ▁total ▁operating ▁re venue ▁per ▁AS M . ▁ ▁So , ▁for ▁instance , ▁in ▁the ▁second ▁quarter ▁of ▁ 2 0 1 1 , ▁South west ▁had ▁scheduled ▁re venue ▁of ▁$ 3 . 8 7 6 ▁b n ▁and ▁total ▁operating ▁re venue ▁of ▁$ 4 . 1 3 6 ▁b n . ▁South west ' s ▁system ▁Pass enger ▁R AS M ▁and ▁Oper ating ▁R AS M ▁for ▁the ▁second ▁quarter ▁of ▁ 2 0 1 1 ▁were ▁therefore : ▁ ▁Pass enger ▁R AS M ▁= ▁$ 3 . 8 7 6 ▁billion ▁/ ▁ 3 1 . 4 5 7 ▁billion ▁= ▁ 1 2 . 3 2 ▁c ents ▁ ▁Oper ating ▁R AS M ▁= ▁$ 4 . 1 3 6 ▁billion ▁/ ▁ 3 1 . 4 5 7 ▁billion ▁= ▁ 1 3 . 1 5 ▁c ents ▁ ▁Again , ▁R AS M ▁compar isons ▁across ▁periods ▁or ▁across ▁air lines ▁also ▁need ▁to ▁be ▁made ▁with ▁care . ▁All ▁else ▁being ▁equal , ▁re venue ▁generally ▁increases ▁with ▁average ▁stage ▁length . ▁However , ▁re venue ▁generally ▁does ▁not ▁increase ▁as ▁quickly ▁as ▁stage ▁length , ▁meaning ▁that ▁R AS M ▁typically ▁decre ases ▁as ▁average ▁stage ▁length ▁increases . ▁ ▁At ▁constant ▁prices , ▁world ▁air