In airline loyalty programs, your mileage balance and lifetime flight miles represent two very different metrics. Your mileage balance (often called "redeemable miles") is the current total of miles available in your account that you can spend on award flights, seat upgrades, or other partner rewards. These miles can be earned through flying, credit card spending, or shopping portals, and they often expire if there is no account activity for a certain period. In contrast, lifetime flight miles are a cumulative record of the actual physical distance you have flown on that specific airline (and sometimes its close partners) since joining the program. These miles are used exclusively to determine "Million Miler" status and are never "spent." They do not include miles earned from credit cards or bonuses—only "butt-in-seat" miles. While your mileage balance fluctuates as you earn and spend, your lifetime total only goes up, serving as a permanent record of your loyalty that can eventually lead to lifetime elite status benefits that never expire, regardless of your future flying frequency.