You should consider travel credit cards to earn miles or points and redeem them with any airline you want, including Volaris. For example, the Discover it® Miles credit card will allow you to earn 1.5x miles on all purchases. What is more, Discover will match all the miles you’ve earned at the end of your first year (if you are a new cardmember). For example, if you earn 30,000 miles, you get 60,000 miles. This card comes with no annual fee and no foreign transaction fee. Another credit card you may want to consider is the Barclaycard Arrival Plus® World Elite Mastercard® credit card with unlimited 2X miles on every purchase. You will receive 70,000 bonus miles after spending $5,000 on purchases in the first 90 days.