In the quiet arithmetic of loyalty, Delta Air Lines and Hyatt Hotels have chosen each other — a long-term partnership announced Wednesday that reshuffles the alliances binding frequent travelers to their preferred brands. Hyatt, departing its enhanced arrangement with American Airlines, signals that in the competition for high-value customers, alignment matters as much as product. The realignment reminds us that loyalty, even in commerce, is not permanent — it is earned, renegotiated, and sometimes surrendered to a better offer.