Jonathan Hall Uncovers: Airline miles

Beautiful beaches, warm water and the summer sun - it's all part of Hawaii.

Betsy Lorusso, Traveler
"My brother and sister-in-law travel there often and speak so highly of the island."

Betsy Lorusso was planning to leave her Foxboro home for a Hawaiian vacation, using frequent flyer miles she earned from her airline credit card.

Betsy Lorusso, Traveler
"This was going to be the perfect summer to take a trip."

She regularly checked her mileage statement and had over 100,000 miles built up in her account. But then one month when she got her statement, she noticed something odd.

Betsy Lorusso, Traveler
"I got an e-mail stating that I had zero frequent flyer miles"

It turns out there was a change in policy. Miles expire, "24 months after a member's last qualifying activity, rather than at the end of the year."

In Betsy's case, she thought she was safe through December, but instead, she noticed her miles were gone in February.

Betsy would have had to scroll through her online statement update and read the fine print, but she missed it and it cost her big time.

Betsy Lorusso, Traveler
"I think if they're going to change the rules they should have put in right in their headline that, ‘We're changing our rules, we're taking your miles away.'"

Betsy contacted the airline to try and plead her case, but she got a firm answer.

Betsy Lorusso, Traveler
"They said, ‘I'm sorry, but we've changed our rules and it's happened to a lot of people and this is the rule and we're sticking to it.'"

It's completely legal for airlines to change the terms of service for frequent flyer programs, but they must comply with consumer protection laws. That's where it can get a little dicey.

Anne Banas, Executive Editor, SmarterTravel.com
"They have the right to change their policy at any time, so unfortunately, it's up to the consumer to know when their miles expire and what they have to do to prevent those miles from expiring."

And travel experts say in this tough economy, airlines are taking advantage of their ability to change the rules.

Anne Banas, Executive Editor, SmarterTravel.com
"What the airlines really want is paying customers. They don't want to be giving away anything for free."

Unfortunately for Betsy, she learned that the hard way.

Betsy Lorusso, Traveler
"By taking the miles away they're punishing me."

So if you have frequent flyer miles, here's what you do to keep them safe: Pay close attention to your monthly statements, because that's where any changes to the policy will most likely appear. In some cases, airlines will allow you to buy back expired miles. And while most airlines will give advanced notice of policy changes, they are not required to, so always double check your miles before planning a trip.