Consumer Reports looks at airline frequent-flyer programs

LOS ANGELES (KABC) -- More than 300 million people belong to frequent-flyer programs, stashing away miles in hopes of a free flight. It's no secret that with limited seats and blackout dates, using those miles can be frustrating. But who doesn't want to fly for free, and can you really get to where you want to go using your frequent-flyer miles?

To find out, Consumer Reports asked staffers to try booking round-trip tickets using their frequent-flyer miles with nine programs: Alaska, American, Delta, Frontier, Jet Blue, Southwest, Spirit, United and US Airways.

They searched for a seat on the five most popular U.S. routes for flights that departed in three days, one month and three months.

"Options were often limited," Mandy Walker of Consumer Reports said. "Our results are just a snapshot in time, but we had the most choices on Delta, followed by Southwest and US Airways."

The deals also varied widely.

"Spirit required the most miles for the routes we checked, followed by US Airways," Walker said. "And they both charged the highest booking fees, more than $100 for last-minute travel."

The best mileage deals were with Alaska Airlines, followed by JetBlue, American, and Delta.

And Consumer Reports found you are usually far better off booking early.

For example, on Southwest's Chicago to New York route, a round-trip ticket went from around 17,000 miles a month before departure to more than 77,000 for a flight three days away.

"On short notice, United was the only one that sometimes lowered the number of miles needed to book a seat," Walker said.

Whatever you do, Consumer Reports says don't hoard frequent-flyer miles. You run the risk they'll expire. And if you can't book a seat using miles, try calling the frequent-flyer service desk. Agents can sometimes find seats that you can't.