The U.S. government needs to review consumer complaints that millions of frequent flier miles are being erased without notice because of confusing agreements, says a New York senator.

Charles Schumer wants to establish industry rules for frequent flyer programs that are billed as a free benefit to help attract and retain customers. There are few restrictions now on how airlines can manage and redeem the miles.

Schumer said he suspects consumers are actually paying for frequent flyer programs through air fare and fees. If so, he said, rules are needed to protect consumers. He's asking the Department of Transportation to review the complaints.

"As the holiday travel season approaches, we cannot let airlines and credit card companies continue to fly off with hard-earned frequent flyer miles," Schumer said Sunday. "When a consumer accumulates valuable frequent flyer miles, they should not have to constantly worry that they are going to expire with little or no notification from the airline."

Ten trillion unused frequent flyer miles worth $165 billion US are in circulation now, Schumer said. But 20 per cent of them may never be redeemed, he added.

Frequent flyer model programs began 20 years ago, most with no expiration dates for the benefits. In the last decade, airlines have created three-year windows for consumers to use the miles, Schumer said.

InsideFlyer magazine finds the lack of consumer protections on frequent flyer miles a common concern. Complaints include miles expiring without clear notice and a frequent change in the value of the miles, according to magazine spokeswoman Michelle O'Neill.

Other complaints include confusion over how many miles can be accumulated for certain trips, O'Neill said.

The Air Transport Association, a trade group for airlines, said each air carrier tailors its frequent flyer miles programs as it sees fit, often based on consumer interest. The group has seen reports of consumer complaints but doesn't track them. The system hasn't been targeted by regulators, it points out.

The group says frequent flyer programs remain popular with consumers and airlines try to make their programs as lucrative and consumer friendly as possible to attract and retain customers.