Passengers at U.S. carriers including American Airlines and United Airlines are burning through record numbers of frequent-flier points to avoid paying higher fares, and the companies couldn't be happier.

Not only are the airlines adding surcharges of as much as $100 on frequent-flier tickets, but getting rid of unused awards — sometimes by raising the number of points required for flights — eliminates millions of dollars in liabilities for them. Other payoffs include deeper customer loyalty and more money from credit-card companies.

"More points and higher fees are an easier way of essentially charging more for the reward ticket," said Jay Sorensen, who helped run Midwest Airlines' awards program and is now president of consulting firm IdeaWorks in Shorewood, Wisconsin. "Credit-card companies are happy when people earn more points, and the airlines are happy when people use them."

Redemptions in 2008 are running ahead of last year's pace, when airlines distributed a record 10.9 million free trips.

The free seats have become more attractive to fliers because domestic ticket prices are up 20 percent to 40 percent at the major airlines this year, according to FareCompare.com. The higher fares are a reaction to surging fuel costs that contributed to $17.1 billion in losses at the country's five largest full-fare airlines in the first and second quarters.

"It makes no sense to sit on these miles anymore," said Dan Berman, 46, of Atlanta, who has redeemed 350,000 points from Delta Air Lines Inc. in 2008.

Buying a one-way coach ticket for a 6,400-mile flight to Tel Aviv would have cost $3,000 in cash, so turning in 80,000 points — worth about $800, by Berman's calculation —"was a bargain," he said, even if it cost just 50,000 points for round-trip overseas flights a couple of years ago.

Should oil prices decline and carriers reduce fares, passengers may revert to hoarding frequent-flier points, said Bob Soukup, managing director of marketing for Northwest's WorldPerks program.

"If the ticket prices are low, people aren't willing to spend even 25,000 for an award ticket," he said. "When fares are up, especially to the more popular destinations, people are more willing to part with some more miles."