Refer to the input text as context and select the correct relationship between 'SkyMiles' and 'Delta Air Lines' from the available options.
Options: manufacturer, operator, developer, stock exchange

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.
operator