Whether they like it or not, travelers have become used to the fact that many airlines now reward frequent-flier miles based on how much your ticket costs: the more you spend, the more miles you get. But Spirit is flipping that idea on its head, and will instead offer bonus miles to customers who buy the cheapest fares — for a limited time.

Spirit’s promotion is only good through August, but it will give customers who buy tickets with a base fare of $75 or less 1,000 bonus miles. If you’ve paid to become part of the airline’s “$9 Fare Club,” you’ll get 2,500 miles.

Spending more than $75? There are bonus miles for you, too:

Bonus miles are in addition to the miles a traveler would usually earn for a Spirit flight, as the airline still hands out miles based on distance flown (along with Alaska Airlines and Frontier). You’ll have to be in the top tier of Spirit’s frequent-flier program to get full value, however. Other members will earn 50% of the miles flown.

This is a clear dig at Spirit’s competitors like American, Delta, United, Southwest, JetBlue, and Virgin America, which all reward points based on fares.

“We want to fly in the face of changing loyalty programs and reward customers for saving money, not spending it,” Bobby Schroeter, Spirit’s VP of consumer marketing , said in a statement.

If you’re interested in partaking in the promo this month, you’ll have to register before you book any flights.

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