In 2026, you generally cannot transfer miles directly from one airline's frequent flyer account to a different airline's account (e.g., you cannot move miles from Delta SkyMiles to United MileagePlus). However, you can redeem miles across partners within the same alliance. For example, if you have miles in a British Airways account, you can use them to book a flight on American Airlines because they are both members of the oneWorld alliance. There are a few rare exceptions where airlines share a common "currency," such as Avios, which can be moved freely between British Airways, Iberia, Qatar Airways, and Aer Lingus. Additionally, the most flexible way to "transfer" in 2026 is through transferable credit card points (like Amex, Chase, or Citi), which allow you to choose which airline to send your points to, effectively acting as a bridge between otherwise separate airline programs.