(MONEY Magazine) – This was supposed to be the year of one-stop online shopping for airline tickets. No longer would we have to slog through countless websites to find the best deal, we were told. We could simply go to Orbitz, the now three-month-old website owned and operated by the five largest American airlines, and get access to every available air fare and (as the slogan goes) "the most low fares to Planet Earth." And if we weren't satisfied that Orbitz had gotten us the best price, a new breed of website had entered the scene: the so-called aggregators, which promised to scour scores of travel sites faster than you can say "resume your upright positions."

Unfortunately, it's not that simple. Some of the newcomers are worthwhile, but there's still no such thing as a site that always gets the best price and makes all other sites redundant.

So what's a savvy traveler to do? We feel strongly that endless hunting for the best of all possible fares is a case study in diminishing returns. None of us has an unlimited amount of time to spend clicking through site after site trying to outwit the airlines' sophisticated yield-management computers. And $10, $20 or even $50 in savings isn't always worth the effort if it requires hours or seriously compromises your travel plans.

That's where this article comes in. After several weeks spent testing top travel sites, both old and new, we devised an online search strategy that makes the best use of your time--and is adjustable to every online air-fare shopper, from the reasonably frugal flier to the hard-core bargain hunter to the obsessive who won't be happy with anything but the lowest fare on the plane. Keep in mind that this system assumes you know where you want to go (30% of online bookers let a good deal determine their destination) and that you're planning your trip at least two weeks in advance (for the best last-minute fare sites, see page 141).

One last thing: You'll notice that we don't mention Priceline.com or other sites that don't give you all the flight details before you commit to a purchase. That's because we've seen too many people end up sorry they ceded that degree of control.

Here's the flight plan, along with estimated time spent on each "leg." Hop off when you want, confident that you've found the best fare for you.

LEG 1: The savvy flier (cruising time: 30 minutes) We think everyone should check Travelocity (www.travelocity.com), Expedia (www.expedia.com) and Orbitz (www.orbitz.com)--in that order. Truth be told, we were tempted to say that Orbitz is the only site you need for finding published fares. Because it gets its flight data directly from 450 airlines (while Travelocity and Expedia get theirs through intermediaries), Orbitz does seem to offer the most flight and fare options for nearly any given travel schedule. Plus, our own testing found that Orbitz often--though not always--had the best prices available.

So why bother with the others at all? Two reasons. First, Travelocity and Expedia still negotiate directly with airlines for discount fares, most of which won't show up on Orbitz. Second, and more important, they offer key search functions not available on Orbitz (at least not yet). Travelocity, in particular, excels by allowing you to search for the least expensive times to fly to a given destination if you are flexible about when you'll travel. Orbitz, by contrast, requires that you start by specifying travel dates.

Once you decide when to travel, we suggest you run the dates through Orbitz anyway. Because Expedia and Travelocity typically charge airlines a $10 sales fee, Orbitz frequently came in $10 cheaper in our testing--not a major saving, but perhaps worth a few minutes.

LEG 2: The hard-core bargain hunter (cruising time: 20 minutes) Many online travel sites--they're often called consolidators, though they generally don't use the term themselves--buy blocks of seats from airlines at a steep discount and sell them to the public for below retail. These "unpublished fares" (so-called because airlines don't want to compete with their own tickets, so they impose advertising restrictions on these fares) generally won't appear on Travelocity or Expedia and never show up on Orbitz. Our favorite consolidators are also the biggest:

Lowestfare.com (www.lowestfare.com) and CheapTickets.com (www.cheaptickets.com). Keep a few caveats in mind: Consolidator tickets are generally nonrefundable and can't be changed or applied to frequent-flier programs.

LEG 3: The obsessive (cruising time: 10 minutes) Aggregators like Farechase.com and Sidestep.com promised to be the online fare-shopper's dream come true: They search every conceivable travel site, thereby guaranteeing the best fare available in only one step. Unfortunately, we found these sites to be excruciatingly slow and in some cases flagrantly wrong: One person searching for a flight to Australia couldn't turn up a single fare, good or bad. But for those who will be satisfied only by a global search, we did find Qixo (www.qixo.com) to be the best of the bunch, both for its relative efficiency and ease of use and because it consistently did better than the other aggregators in our testing. In one case it found an $845 round-trip fare from New York City to Beijing. Travelocity's best fare was $1,595, Expedia's $1,052.