Mileage-award credit cards: our top picks.

Some credit cards promise free tickets on any airline without blackout dates or mileage-award seat limitations. Others hook you with thousands of sign-up bonus miles or double or triple miles for charging routine purchases such as groceries.

All those juicy deals sound good, but what you really ought to know is which mileage-award card is the fastest route to a free ticket. To find that ideal card, we researched the field and found that three major types of cards grant award travel, and the best one for you depends on your buying and flying habits. Here is a list of the card types, their pros and cons, and the top choices in each category.

AIRLINE CARDS

Pros: These co-branded cards can be the fastest track to a free ticket if you fly several times a year on the same airline and charge everything that you can on the card. Many of these cards grant double miles for charging routine purchases from, say, pharmacies or hardware stores. And some, such as the United Mileage Plus Gold Class card, offer tempting sign-up bonuses that are nearly enough for a free ticket. Although there are usually caps on the miles you can earn annually (typically 50,000 to 100,000), bonus miles aren't counted in that total.

Cons: If you carry a balance, the costs of these cards can erase the value of their rewards. Annual fees can top $100, and interest rates--typically the prime rate plus 9.99 percentage points--may be double those of other cards, according to CardWeb.com, a card research and information service. What's more, airlines typically limit award seats and impose blackout dates.

Top pick: The American Express Delta SkyPoints card program has no seat limits or blackout dates and lets you trade in points for discounts against the first $500 of a ticket's price. That's a big plus if you don't have enough points for a free trip. Discounts range from 10 percent for 3,000 points to 75 percent for 20,000, getting you a $500 ticket for only $125. The $49 fee is waived the first year, and you get 2,500 sign-up points.

BANK CARDS