Arlington resident Jayson Jones was caught off guard last week when a United Airlines ticket agent charged him $25 each way to check both a suitcase and his golf clubs for his flight to Billings, Mont.

That was on top of the $39 he paid to sit in the "economy plus" section and make the ride more bearable for his 6-foot-7-inch frame.

Welcome to the new reality of travel, as airlines look to mitigate crippling fuel costs by charging for things that used to come with your ticket.

Starting Monday, most major airlines began charging $25 for a second checked bag to domestic passengers who aren't elite frequent fliers or sitting in premium class. American Airlines added a similar fee that begins next Monday.

United increased its penalty for changing itineraries from $100 to $150 on domestic routes and reinstated a Saturday-night stay requirement for discounted fares. US Airways began charging extra for window and aisle seats – something Northwest Airlines has been doing on domestic routes since 2006 and recently expanded to international itineraries.

Northwest also increased its fees for unaccompanied minors – charging as much as $100 each way for trips that require a connection.

On top of all this, the airlines have announced 10 major fare increases in 2008. Data collected by Southlake-based Travelocity shows that airfares this summer are 12 percent higher on average.

"It just seems like we're being nickeled and dimed to death," Mr. Jones said.

"The customer today really has to be on their toes," said Tom Parsons, president of Arlington-based Bestfares.com, adding that even he was caught off guard recently by overweight bag charges that had gone up to $50.

Mr. Parsons encourages fliers to weigh their bags on a bathroom scale before and come up with a plan to shift things around if a bag is over the limit at the airport.

Ray Cox, a Dallas teacher who paid extra for overweight bags on a recent trip from Spain, said keeping track of the fees gets frustrating.

"You really have to read the fine print," he said. "I'd rather pay a higher [airfare] price than having to worry about all these other fees."

Rick Seaney, chief executive of Dallas-based FareCompare .com, said he expects more of the same as airlines attempt to remake their financial models.

"You can rest assured that every bean counter at every airline is looking at everything they can possibly charge for," he said.

For travelers, that means looking beyond airfares when considering trip costs. It may even mean learning to pack differently.

"I'll definitely be packing lighter," said Mr. Jones, who said he's used to checking two bags when he travels.

In addition to the second bag fee, Fort Worth-based American Airlines increased fees for additional bags. Passengers will pay $100 for checking third, fourth and fifth bags, and the fee jumps to $200 a bag after that.

Charley Wilson, a spokesman for American, said full-fare passengers, first- and business-class fliers, military travelers and most international fliers are exempt from the free bag allowance. The airline estimates that about 4 percent of passengers who check a second piece of luggage will actually pay the fee.

Mr. Wilson said the rule change could generate "tens of millions" of additional revenue and is just one way the carrier is trying to offset record fuel costs. Officials from United Airlines estimated that its second bag charges would generate $100 million in annual revenue.

Dallas-based Southwest Airlines hasn't instituted the $25 fee but did reduce its free bag allowance from three bags to two in January.

Last fall, Southwest launched Business Select airfares, which charge a premium for extras such as boarding in the first group, a free cocktail and an extra Rapid Rewards frequent flier credit. Last week, the airline started charging its first fees for nonalcoholic beverages when it started selling Monster energy drinks on flights.

Spokesman Chris Mainz said Southwest is taking a different approach by focusing on new products and services that customers are willing to pay for.

"I don't think you'll see us charging for things that customers have always had as part of the package on Southwest," he said.

Some new charges and increases to watch for:

•$25 for a second checked bag on most major airlines.

•$100-$200 per bag for more than two checked bags.

•$50-$100 for bags that weigh more than 50 pounds.

•$150 to change itineraries on United Airlines.

•$75 each way for unaccompanied minors on Northwest Airlines nonstop flights; $100 each way with a connection

Some airlines have started charging for window seats, advance seat assignments, early boarding and even bottled water.

Suzanne Marta