Denver-based Frontier Airlines has made the leap to becoming an international airline, instituting service to Cancun on Dec. 21 and to Mazatlan a day later. Frontier will operate one daily non-stop flight between Denver and Cancun, and twice-weekly service, on Wednesdays and Saturdays, between Denver and Mazatlan.

And here’s the frequent-flying rub: EarlyReturns members will earn double miles for travel to and from Cancun and Mazatlan until Feb. 12. In the long term, members will be able to earn a free roundtrip ticket to and from Cancun and Mazatlan by redeeming 25,000 miles (Remember, though Frontier may be geographically limited, its 15,000-mile domestic roundtrip award is hard to beat).