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.
What is the relationship between 'SkyMiles' and 'Delta Air Lines' in the context of the input sentence.
Options: operator, developer, stock exchange, manufacturer