Like the federal reserve, airlines issue currency—points—out of thin air. They also get to decide how much that currency is worth and what it can be spent on. This helps explain why the points system feels so opaque and, often, unfair. Online analysts try to offer estimates of points’ cash value, but airlines can reduce these values after the fact and change how points can be redeemed. Airlines even sell points at above their exchange-rate valuation, meaning that people are paying for something worth less than the money they’re buying it with, in part because it’s so hard to know what the real value is.