It is a surprising reality of modern aviation that major airlines often make more profit from selling miles than they do from flying passengers. Airlines have essentially become massive financial services companies with a "flying wing." They sell miles in bulk to banks (like Chase, Amex, or Citi) for roughly 1 to 2 cents per mile. These banks then distribute those miles to consumers as rewards for spending on co-branded credit cards. Because the airline's "cost" to fulfill a mile (when a passenger redeems it for a flight) is often lower than what the bank paid for it—and because many miles go unredeemed or expire—the "breakage" creates a massive, high-margin revenue stream. For example, during financial downturns, airlines like Delta and United have used their frequent flyer programs as multi-billion dollar collateral for loans, proving that the "loyalty program" is often their most valuable asset. Additionally, airlines earn revenue from miles through "partner" redemptions, where they charge other airlines or retailers when you use your miles for their services. This ecosystem has turned frequent flyer programs into the financial engine that keeps airlines afloat even when fuel prices or ticket sales are volatile.