Delta Air Lines will radically change its SkyMiles frequent flier program next year, becoming the first of the "big three" U.S. airlines to ditch a fixed miles-for-a-free-flight system in favor of a supply-and-demand scheme that may require more mileage points to fly on more popular routes.
Take context from the input text and decide on the accurate relationship between 'SkyMiles' and 'Delta Air Lines' from the options provided.
Options: stock exchange, developer, manufacturer, operator