A bizarre truism about frequent flyer miles is that the easier they are to get ahold of, it seems, the harder they are to use.
But some airlines' frequent-flyer miles programs are friendlier than others, and according to a newly released survey by the IdeaWorksCompany, flyers intent on redeeming rewards are more likely to have success on already value-oriented airlines.
The Switchfly Reward Seat Availability Survey ranked airlines' frequent flyer programs based on a number of factors, including the number of roundtrip seats each airline had available for rewards members and the average prices of their tickets, to determine which major airline had the best program.
For domestic travel, the company ranked Southwest Airlines' "Rapid Rewards" program as the best frequent flyer program for 2013. Internationally, GOL Airlines and Air Berlin both tied for first place.
According to the survey, the worst domestic airlines for redeeming frequent flyer miles are Delta Air Lines and U.S. Airways. Turkish Airlines came in last place among international airlines.
In an interview with the Wall Street Journal, Jay Sorensen, president of IdeaWorksCompany, said the large differences in reward ticket availability is "not accidental" and that some airlines "consciously provide more award seats."
Sorensen also mentioned that travelers are more likely to successfully book a ticket using frequent flyer miles by calling the airline on the phone instead of visiting an airline's website.
Watch Sorensen's interview with the Wall Street Journal above, and see the full rankings and complete methodology here.