Frequent flier miles can be a wonderful thing—if you can use them. 

Many travelers rack of tens of thousands of miles looking forward that dream vacation only to be told their desired dates are unavailable or that ticket to Bora Bora is now double the price.

Airline research firm IdeaWorks Company has been analyzing domestic and global carrier mileage programs for five years. Their latest annual Switchfly Reward Seat Availability Survey is based on 7,000 booking queries made by the on the websites of 25 frequent flier programs during March of 2015 with travel dates from June to October of this year to find out how much flexibility consumers really have when cashing in on their rewards miles. 

To test availability, IdeaWorks tried to book travel on 280 specific dates per airline, using only rewards travel. Each itinerary in the test phase included a Saturday night stay.

So which airlines have the best rewards programs?

Southwest came out on top among U.S. airlines—tying with Germany's airberlin for the top spot overall—with 100 percent availability for all of the requested travel dates. JetBlue was the next best U.S. carrier with a 92.9 percent availability.

Not only did Southwest have 100 percent availability, but their average price for a rewards ticket was significantly less than most domestic carriers, averaging about 9,400 points for a trip ranging between 250 and 2,500 miles. That same trip would cost you over 27,000 American AAdvantage mileage points.

“Consumers expect something of value from brands in return for their business and for their loyalty, and they want and expect offers that are relevant reflections of themselves,” said Switchfly CEO Daniel Farrar in a press release. “The key takeaway is that airlines can’t afford to allow a single customer to have a bad experience anywhere in the booking or redemption path.”

Customers with a lot of Delta Skymiles may want to look into travel as soon as possible. Delta’s program received the lowest domestic availability score at just 57.9 requested dates were available to book with miles.

Check out the full survey to see how your preferred carrier measures up to the competition.

Overall  Reward Availability – Top 5

1. airberlin – topbonus - 100% (tie)

1. Southwest – RapidRewards – 100% (tie)

2. Virgin Australia – Velocity – 96.4%

3. Air Canada – Aeroplan – 90.7%

4. Singapore – KrisFlyer – 90%

5. JetBlue – TrueBlue – 87.1% (tie)

5. Lufthansa/SWISS/Austrian – Miles & More – 87.1% (tie)