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Frequent travelers are frequently frustrated by their inability to book a reward seat because the flight they want to take has no more reward seats available — if it ever had any in the first place. But as with most things, travelers have choices and there are airlines that have a solid record of making reward seats available to their frequent passengers.

Following a March survey of 25 carriers, during which consulting firms IdeaWorksCompany and Switchfly made 7,640 attempts to book a reward seat, the firm found only two carriers that offered 100% seat availability for frequent flyers: Air Berlin and Southwest Airlines Co. (NYSE: LUV).

The CEO of Switchfly noted:

Value-oriented airlines continue to lead reward seat availability but network carriers continue to improve as sweeping changes across loyalty programs affect the mega-carriers’ most loyal members. This is certainly good news but it will remain incumbent on travelers to search for redemptions that capture the greatest value as airlines continue the sea-change toward operating their loyalty programs as profit centers.

The average survey score among the six low-cost carriers was 95.8%, while traditional carriers scored 65%. JetBlue Airways Corp. (NASDAQ: JBLU) scored 92.9% availability, and Brazilian carrier GOL Linhas Aereas Inteligentes S.A. (NYSE: GOL) scored 90.7%.

The best U.S. legacy carrier was United Continental Holdings Inc. (NYSE: UAL) with a score of 71.4%. The two carriers that just merged to create American Airlines Group Inc. (NASDAQ: AAL) scored 55% (American) and 35% (US Airways). Delta Air Lines Co. (NYSE: DAL) also scored 55%.

Last winter Delta announced that it would adopt a revenue-based reward program beginning in 2015, replacing the distance traveled with the fare paid to determine awards. Under the new program, points will be awarded for dollars spent combined with the frequent-flyer status of the traveler. Infrequent travelers will not accrue rewards at nearly the same rate as they do now, while frequent flyers will accrue rewards far more quickly.

That may make sense from a carrier’s point of view. After all, rewarding your best customers pays off better than rewarding your occasional customers. But if the value players like Southwest and JetBlue stick with the exiting miles-flown rewards programs, they should pick up more of the infrequent travelers who now fly with the legacy carriers. The results of Delta’s new rewards plan will be interesting to say the least.

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