"In what other industry is it okay to give discounted “girl tickets”?" To provide, at least, an objective answer, airlines will discount tickets if they have a

"In what other industry is it okay to give discounted “girl tickets”?" To provide, at least, an objective answer, airlines will discount tickets if they have a given level of certainty that the passenger is female -- except, interestingly, on Thanksgiving and Mother's Day, when female demand is higher than male demand.