Background
American Airlines AAdvantage miles typically expire after 18 months of inactivity.
Answer
To prevent your American Airlines miles from expiring, you can keep your account active by earning or redeeming miles. This can be achieved by taking a flight with American Airlines, its partners, using an American Airlines credit card, shopping through the AAdvantage shopping portal, or renting a car through partner rental agencies. By regularly engaging in these activities, you can ensure your miles remain active and do not expire.