Capital One miles are among the most flexible travel rewards in 2026 because they can effectively be used for any airline in the world through two distinct methods. The first is the "Purchase Eraser" feature: you book a flight directly with any airline or third-party site using your Capital One card, and then use your miles as a statement credit to "erase" that charge within 90 days at a flat rate of 1 cent per mile. This allows you to fly on boutique carriers or airlines that aren't part of major alliances. The second method is the Transfer Partner system, where you can move miles to over 15+ loyalty programs (like Air Canada Aeroplan, British Airways, or Turkish Airlines) at a 1:1 ratio. While you cannot "transfer" directly to US domestic giants like Delta or United, you can use the alliance partners (e.g., transfer to British Airways to book an American Airlines flight) to reach almost any destination globally with high point-to-value efficiency.