Frontier offers one co-branded credit card through Barclays that you can use to earn Frontier miles. Frontier is not partnered with any program, so this is the only way to earn Frontier miles.
Frontier is not a direct transfer partner of any program which means there's no way to earn Frontier miles outside of using the Frontier Mastercard. If you're looking for an alternative option, I highly recommend looking at the Capital One Venture & Spark Rewards program.
Miles earned with Capital One's cards have the same baseline value as Frontier miles except that they can be redeemed for 1 cent in value towards any kind of travel. So not only can use you use them for Frontier, but you can also use them for any other airline, hotels, car rentals, parking fees, tolls — you name it.
