American Airlines Vacations offers up to 5,000 AAdvantage miles for free when you book select 3-day Avis car rentals. Plus, receive up to 35% off every Avis rental. That's the first such offer we've seen from American Airlines and Avis. The miles will be credited to your account six to eight weeks after the end of the promotion. Rentals must be booked and completed by August 31.