Good. Bad. Better. Best. Most airline loyalty programs have been called all those things. And more. But they can't all be the best. Or even the worst. So which program is the best? And why?

In the minds of many travelers, the critical measure of an airline mileage program's value is the time it takes to earn a free ticket. Shorter is better. And the shortest is the best.

There are two approaches to measuring the speed at which a mileage program converts a consumer's loyalty into free flights. The first looks at the depth and breadth of a program's partner roster. The theory: The more opportunities a program offers to earn points, the faster will be a member's progress toward earning an award.

So a program that awards points for flights on multiple airlines, hotel stays, online shopping, mortgages and dining out is assumed to offer a shorter route to awards than one that only awards points for flights on a single carrier.

Evaluated on those terms, the legacy carriers' schemes enjoy a clear and commanding advantage over the programs hosted by the discount carriers.

American's AAdvantage program, featuring hundreds of companies that award miles, is a case in point. The partner lineup includes an assortment of allied airlines, most major hotel chains and car rental companies, mortgage and finance companies, a network of more than 200 Internet retailers, and so on. AAdvantage members can earn miles for many everyday purchases, not just for travel-related activities, making awards more attainable.

The discount carriers occupy the opposite end of the spectrum. Members of JetBlue's TrueBlue program are limited to earning points for JetBlue flights and for charges to a program-affiliated credit card. And while Southwest has expanded its program to include a handful of hotels and rental car companies, the earning opportunities are still meager in comparison to those available with the mainline carriers.

American's AAdvantage wins the partner race, giving it bragging rights to the title of "the world's largest program." But the programs of Continental, Delta, Northwest, United and US Airways are of roughly comparable scale, and most consumers interested in increasing their mileage balances with nontravel purchases would be as well served by any of them.

The other approach to judging programs focuses more narrowly on the ratio between earning and redemption — how fast points are earned, and how many points are required for an award.

This is where the discount airlines stake their claim to superiority. AirTran boasts "the fastest free ticket on Earth." Frontier promises that its EarlyReturns program "offers the fastest awards in the industry." And Southwest describes its program as follows: "Rapid Rewards — where you fly free faster."

So, for example, Frontier points out that a free domestic ticket is awarded in its program after just 15,000 miles. Compared to the 25,000 miles required by most other programs, that's a bargain.

In AirTran's A+ Rewards program, members earn one credit for every one-way flight. And eight credits can be redeemed for a free one-way flight. So eight paid roundtrips are required for a free roundtrip ticket.

But the same ratio applies in Southwest's program: Fly eight times to earn a freebie. So it would seem that neither AirTran nor Southwest has an advantage over the other. However, a member of AirTran's program could earn a ticket faster, because it's possible to redeem for a one-way award for half the number of credits required for a roundtrip. So AirTran wins on a technicality.

But practically, since most travelers play the mileage game to earn a roundtrip ticket, AirTran and Southwest are effectively equally generous.

What about Frontier's claim to a faster free flight? How does an award at 15,000 miles compare to an award after eight roundtrip flights? It depends, of course, on the length of the Frontier flights. Someone flying Frontier from Denver to New York or Washington would exceed 15,000 miles after just five roundtrips, handily beating members of AirTran or Southwest's programs to the prize. But for flights under 900 miles each way, a member of Frontier's program would have to fly more than eight times to earn a free ticket, giving the edge to AirTran and Southwest.

The real measure of a mileage program's value may have less to do with the speed to an award and more to do with award availability. After all, if there are no award seats available, it matters little whether it took eight, 10 or more flights to reach an award threshold.

From that standpoint, it could be argued that the best airline scheme is among the newest and smallest, Spirit Airlines' Free Spirit program. Although Spirit follows other airlines in limiting the number of seats available for award redemption, its program boasts "award travel available on every flight, without blackout dates." On the other hand, Spirit's partner roster is limited, and a cross-country award trip is priced at 25,000 miles.

Clearly, there is no single answer to the question of which airline program is best. If there were, all travelers would be members of that program.

Frequent buyers may reach award thresholds faster by taking advantage of the robust earning opportunities offered by the full-service carriers' programs. Frequent fliers may be better served by slimmed-down programs such as those of AirTran or Southwest. Spirit's program might be a welcome alternative for those who have been frustrated by limited award seats. And so on.

What's the fastest way to a frequent-flier award? Final answer: Notwithstanding airlines' claims to the contrary, it depends.

Reach Tim Winship at questions@frequentflier.com