There is requirement of suitable rule for minimum possible fare of a route because if the competition on a particular route is very high, the fare go too low that even at 100% filled seats, overall profit is negative even with most fuel efficient plane. From my view, minimum fare should not be lower than 1/3 of decided fare by system i.e. if decided fare is $180 then lowest fare is $60 or $90 at 1/2 cut-off.