Southwest Airlines makes Rapid Rewards loyalty points harder to earn for travelers who buy its lowest fares, and a bit easier at its most expensive prices.

Southwest quietly altered the earnings structure for three of its four fare classes, slashing the number of points customers can earn for lower-level fares while raising customers’ earning potential for its highest-priced tickets.

"Although we modified some ratios for earning points, Southwest Rapid Rewards remains one of the most rewarding and flexible loyalty programs in the airline industry with unlimited reward seats, no blackout dates, and points that don’t expire for all Members," Southwest said in a statement.