With the Delta Skymiles card from American Express, you earn two air miles for each dollar you spend at supermarkets, gas stations, drug stores, home improvement stores and the U.S. Postal Service.
Of course, you can also earn air miles the old-fashioned way -- by flying. Let's say you book a flight on Delta with your Delta Skymiles card. You'd earn from 500 miles minimum to 150 percent of mileage. It's a great way to rack up air miles.
The price of the perk
The downside of airline credit cards is the price. Annual fees range from $50 to $125. They also tend to have higher-than-average interest rates.
Just look at the US Airways Dividend Miles Visa from Bank of America. It comes with a variable APR of 15.24 percent and annual fee of $50 for a classic card and $70 for a gold card.
Bankrate tracks the best of the frequent-flier credit card deals. Go to our credit card rate table to explore the choices currently offered.
Because of the high interest rates, it's not a good idea to carry a balance on these types of credit cards.
Not keen on the high price of an airline credit card? You have lots of other choices. Hundreds of additional air mile cards promise to reward customers with a free-round trip ticket that can be used on any airline.
"There are so many of those they're difficult to keep up with," Petersen says.
The hook of these generic air miles cards is their flexibility. You earn miles toward free air fare that can be used on any airline. They also tend to have lower fees and lower interest rates than cards associated with specific airlines.
The downside of generic air miles cards is you can't dump the miles you earn with the card into a frequent flyer account.
"You have to earn all your miles on the card," Theoharides says. "There's no combining with a frequent flier account. So it takes a little longer."
Miles on generic cards may not be good for international destinations. Be sure to check this out, especially if you have your heart set on a free trip to Rome.
Some generic cards require 21-day advance notice and Saturday night stay when you book your free flight. So a free last-minute getaway may be out as well.
Before signing up for an air mile credit card, be sure to study the details.
Where can you fly with your air miles? Will they take you to your dream destination? Petersen hears from people who've racked up thousands of miles on a card only to learn it won't take them to the place they most want to go.
"All frequent flier programs are not created equal," Petersen says.
So decide where you'd really like to go, and then shop around for a card and rewards program that will get you there with the least amount of spending.
Make note of mileage requirements and blackout dates. Be sure to check out the list of partners for each frequent flier program. Do you already shop at an airline partner? What kinds of bonus miles opportunities are available? Be prepared to do some digging.
Low APR? What's the catch?
On the credit card side, you'll want to compare the interest rate, annual fee and grace period. Some air-mile card deals are pretty expensive. Some of the lower-priced ones may not be as good as they seem.
And there are plenty of folks out there who should avoid air-mile cards altogether. Because of the high interest rates, air-mile cards are not a good choice for people who carry big balances.
If you don't spend thousands of dollars a year on a credit card or travel frequently, it's going to be awfully tough to earn enough miles for a reward. "Most people don't spend $20,000 on their credit cards -- enough to get a ticket in the first year," Detweiler says. "Most people won't earn the maximum rewards. You have to be realistic about how much you will earn."
Look at your financial situation, and be realistic about how much you can afford to spend on an air-mile card.
"No matter what they tell you in all the fancy literature, these programs are not for everyone," Petersen says. "If you're only spending $1,000 a year, I wouldn't get any of these cards. I would go out and get a fee-free one with a low interest rate."