How much Frontier Airlines miles are worth depends on the redemption methods you select. Using them to book award flights typically offers an average of around 0.9 cents to 1.1 cents per mile. Still, it's possible to get better value with little research, especially if you're flexible with your travel plans. Using your miles for magazine subscriptions is also an option and may provide pretty good value.
You get to earn FRONTIER Miles when you fly with Frontier Airlines, through the FRONTIER Airlines World Mastercard and when you spend with the program's partner merchants.