Delta and Starwood introduced Crossover Rewards, an attempt to share each others’ best customers — they will tell you that Starwood customers fly Delta more and spend more with Delta, for instance. Marriott and United got into the act together.
That’s left American and Hilton as the only remaining possible dance partners. Hyatt has too small a footprint to be the major partner of the world’s largest airline, and IHG Rewards Club doesn’t have a meaningful elite program.