For starters, there are sites which have folded, some new competitors, and sites that changed their model significantly. At the same time, there has been pushback from airlines and suppliers, some of which have resisted the aggregator model. (The lawsuits between American Airlines and Kayak, which initially resulted in American Airlines no longer being listed in Kayak results, was perhaps the most prominent case of pushback. Since October 2008, aa.com results are back in the results. More on that below.)

The result: The golden ring of a truly complete search, covering all the options and all the providers, is still a ways away. No single site actually finds every flight option, every fare, or every seller.

But that doesn’t mean that there aren’t differences between the aggregators. It’s time to disaggregate the aggregators again.

This year, each site was put through multiple tests. Four kinds of itinerary were tested: A large-city to medium-city domestic US flight with multiple carriers offering direct service; a medium-city to small-city domestic US flight with at least one change of plane required; an international flight with a US origin; and international flights (from Paris to Dubai, and Manchester to Madrid) to test how sites do for non-US flights. For each of these flights, I tested a short-term booking (7 days advance purchase) and a longer-term booking (30 days advance purchase).

This time, I compared Kayak, Sidestep, Mobissimo, TripAdvisor Flights, Momondo, Skyscanner, WeGo (formerly Bezurk), Trax, Farecast, Fly.com, and Dohop. Sites which were on the list last time but either folded or stopped doing metasearch include FareChase (bought by Yahoo, then abandoned in March 2009), PriceGrabber, and Qixo.

So which aggregator came out on top in 2009? Here’s the summary, with site-by-site reviews thereafter…

• Overall best bet: TripAdvisor Flights. Low fares, good features, a solid performer overall. It took them a while to join the game, but it’s a strong product with a small but important edge over its closest competitor, Kayak.
• Lowest price, domestic: If you’re searching for domestic US airfare, most of the aggregators did pretty well, but the lowest fares were consistently on TripAdvisor Flights, Mobissimo, Momondo, or Trax. (Kayak and Sidestep would have been included in this list, but they often offered the lowest flights at the same base fares, but typically directed you to Orbitz, instead of to the airline or to a no-fee site like Priceline, to buy the ticket. Orbitz still charges a booking fee as of this writing, so single-airline itineraries can typically be purchased for less elsewhere.)
• Lowest price, international from US: If you’re searching for international flights starting in the US, try Kayak and Trax.
• Lowest price, international, ex-US: If you’re search for international flights that don’t originate or end in the United States, Mobissimo and Momondo performed best.
• Class conscious: If you’re looking for a deal on premium cabin fares, fly.com is your site.
• Sorting features: If you want control over options, and like to tweak and limit your results, Kayak gives you the most power.
• Real total cost: TripAdvisor Flights lets you estimate what your actual costs will be, including luggage checking fees, headphone charges, etc.
• Avoid: WeGo, which offered impressively-low search results, but none were actually bookable. Also avoid Dohop, whose prices were consistently higher than their competitors.

Individual site reviews

TripAdvisor Flights
Although a clone of its competitors in many respects, TripAdvisor’s new aggregator offers one big difference: The site offers an analysis of how much the flight will actually cost you, once you figure in the baggage fees, the headphone fees, etc. It even considers what your elite status is. That’s a great feature. Second, and more disappointingly, the site (unsurprisingly) favors its sister sites Expedia and Hotwire in its results. But those sites add no booking fee right now, so no big whoop. The site combines the best sorting features of Kayak with the added value of fee analysis. TripAdvisor takes it by a nose.

Kayak
Kayak is the largest of the metasearch sites, and it offers solid results. But it didn’t consistently offer the cheapest fare, because the universe of sites it searches is sometimes limited by agreements with individual partners. (American Airlines, for example, won’t allow results from its website to be shown alongside AA flights sold through Orbitz.) Orbitz puts demands on its partners, too, and subsequently, Kayak is heavily Orbitz-centric, with no representation of Expedia, Travelocity, or Priceline. Actual fare availability was good when I clicked through to sellers’ sites. Kayak’s sorting features are still the best (so good that they’re copied wholesale by TripAdvisor), with the ability to narrow search results by time, airline, or aircraft type (e.g., no props or RJs), to name a few. The site has recently added “flight quality warnings,” such as on-time percentages and tight-connection alerts, but those aren’t a big deal.

Sidestep
Kayak bought Sidestep a few years ago, but continues to operate the site as a standalone entity. Frankly, I don’t see why. The results are identical, the search tools are nearly the same, and there’s nothing to recommend this site over its parent. Everything stated above is true here as well, but why bother?

Farecast
Farecast, now owned by Microsoft, is most famous for their fare prediction engine, which suggests whether ticket prices for your route will drop in the future. The predictions are pretty accurate, though they don’t account for times of day, routing, or airline, if you have preferences on those matters. (And you should.) Farecast also offers up an aggregator, albeit a fairly minimalist one with few options and a favoritism for Orbitz results. Come here for the fare predictions, but for live fare comparisons, you’re better off elsewhere.

Mobissimo
Mobissimo claims to search more sites than anyone else, but not necessarily for a domestic US search. They have good coverage of Asian and European airlines, but their controls and filters are less than others’. Decent results, but I preferred others’ display of information.

Fly.com
From the folks who brought you TravelZoo, Fly.com offers one gimmick that’s worth noticing: First- and business class fare comparison. That’s it. Otherwise, it’s a clone of other sites. If you’re not looking for premium cabin seats, skip it.

WeGo (formerly Bezurk)
Big on teasers, low on success. WeGo touts some amazing fares, but good luck buying them. They also don’t list the lowest flight first: They show a sponsored link at the top. Bad, bad, bad.
Update April 9, 2009: WeGo has eliminated the sponsored results feature.

Skyscanner
Britain’s SkyScanner offers decent results for UK-based searches, but it’s not as helpful to others. For US and non-UK searches, SkyScanner searches returned far higher fares than the average.

Momondo
This Danish site is quite good at ferreting out obscure sellers of travel, especially for intra-European itineraries. But be aware that you’ll often get results from suppliers in countries outside the destination or origin. Flying Chicago to Baltimore? Your ticket could be sold by a British company (which could mean a 3% credit card surcharge).

Trax
Trax.com offers a Kayak-lite search that works well for domestic US itineraries. They include Priceline and Cheapoair, which others don’t, but the results weren’t significantly better.

Two other sites of note:
1. An aggregator you can’t use for booking, but which is great for research, remains ITA Software. Their engine powers Orbitz, and backs up Kayak and TripAdvisor results. They’re a great resource. (Click “log in as a guest” to use the search without registering.)

2. No discussion of fare search would be complete without a mention of FareCompare. The site’s alerts give you a heads-up on future sales by notifying you when fares drop, before they go on sale. They offer fare search, too, which is powered by Kayak.

So… what’s your experience with fare aggregators? Hit the comments to share your stories.

Instead of offering a prediction about the direction of room rates, as they do for airfare, the site offers an analysis of how relatively good or bad the rate is. They offer a star rating (1 to 5) for how good the rate is, historically.

That’s helpful, but not a forecast. Essentially, Farecast is now a hotel rate aggregator, comparable to Kayak or Sidestep.

The historical ratings are interesting, but are they really helpful? Depending when you’re trying to book, and depending on occupancy rates, you might not do well to hold out for a five-star rate at the hotel you’re looking at.

A rate prediction might be on the horizon, but I wouldn’t count on it any time soon. The reason may be the variation in rooms. As I wrote in a review of hotel rate aggregators nearly a year and a half ago:

Hotel searches are trickier than airfares, for the most part, because not all rooms are created equal, and hotel location is less standardized than air travel routes. Finding a low rate isn’t helpful if you have strong preferences for two queen beds vs. one king bed, or smoking vs nonsmoking, or if you need to be within walking distance of a particular location.

Add to that the large blocks of rooms that can be taken up by conventioneers, wedding parties, or any other large group.

Knowing that rates are good or bad may make you feel better or worse about your reservations, but will they stop you from making the booking? After all, most hotels will let you cancel and re-book if a new, lower rate appears.

Ironically, this comes on the heels of the Seattle Times’ review of Farecast today. The newspaper found that the service was accurate in predicting the direction of fares in 61% of the searches queried. That’s below the firm’s target of 75%, but above my earlier (limited) assessment of around 50% accuracy.

So how does the new insurance/guarantee work? Much like buying a stock and purchasing a put option to protect you in case of a drop in the price, Farecast will sell you a “policy” when they predict the price will drop or hold steady. (If they predict the price will rise, then presumably you’ll be buying the ticket anyway. VentureBeat explains:

Let’s say you’re planning a trip, say to Kansas on Dec 5, and Farecast shows a low price of $210 and further, predicts prices are going to drop over the next few days. Now, rather than waiting, you can buy something called a “Fare Guard,” which lets you lock into any subsequent price drop automatically. Initially, the product will come at a promotional price of $1, but later might be priced around $10. Once you buy the Fare Guard, you have seven days to buy the actual ticket. If the price does drop, you get your savings. If it goes up, unexpectedly, you can buy the ticket, and Farecast will refund you the difference — so you win either way.

It’s an interesting idea, and the insurance is attractively priced (especially at the $1 intro rate). But remember, the contract covers THE LOWEST fare on the day you’re buying. Not the preferred time, airline, or connection. (Sounds like bidding for a ticket on Priceline!) There is thus a bit more variation and risk than first seems obvious.

The feature is still in beta, but readers who want to try it can participate in the test by clicking here and using one of the following beta-preview password combinations:

username: venturebeat
password: fareguardtest

username: johncook
password: fareguardtest

If you try it, please report back with your experience!

Maybe this will be the start of a market in a whole range of airfare derivatives. I’d like to short 20 Thanksgiving tickets to Los Angeles, sell puts on the July Paris contracts, and put a straddle on my December Newark itinerary.

Related:
- Farecast expands price predictions to over 50 cities
- Farecast beta goes public, just in time for a reader review
- So how accurate is Farecast?

I travel with relative infrequency, say 3-4 times per year. When I do, I /always/ fly American Airlines because I like their planes, I like their service, and, usually, I like their price. The latest factor keeping my business with them, however, is the availability of $30 500mi upgrades when using Kiosk Check-In. I LOVE it. It’s cheap, fast, and the only way I’ll ever qualify to upgrade from the N or Q class fare I normally book. My question is this: is there any online tool which will let me view historical loads so that I can book flights which normally have room left up front?

The upgrades-for-purchase at check-in can be a decent deal, especially if you’re on a super-cheapo ticket. To maximize your odds of being able to buy one, you want to be on flights with 1) lots of tickets for sale in first class (which is hard to predict, but you can see tickets for sale up until a few hours before the flight) AND 2) with the fewest possible number of top-tier elites on board. These elites might be automatically upgraded by the airline, so they’d jump ahead of you, Trey. But unless you work for the airline, there’s no way to know who’s booked on a flight, though you can expect super-elites to travel to business destinations from main hubs, say, Dallas-New York.

I’m afraid I don’t know of any online service that offers reliable historical information about how many actual seats were available for upgrades into first class. The closest thing out there is UpgradeSuccess.com, which I’ve mentioned here, but the information in their database is pretty thin.

Other sites like ExpertFlyer let you subscribe and see loads for FUTURE flights, but that doesn’t tell you how these flights filled up in the past. FareCast collects this sort of information and gathers it in their database to make predictions about future fares, but again, this isn’t necessarily data that would help you in picking an easily-upgradable flight.

But maybe I’m missing something: Someone out there will surely correct me if I’m wrong. Any ideas?

Farecast, the site that intends to predict the directions of airfares for your specific travel dates, has expanded their beta site to include many more airports.

The horizon for predictions is limited to 3 months. If you’re looking at travel dates more than 3 months ahead, you won’t get any analysis, just fares.

It’s also still a bit buggy. I had a few searches come up with no flight results, or no prediction, even though they were in the range of “legal” dates.

Predicting airfares’ direction is tricky business, since fare wars are waged by humans, not machines. Plus, fuel prices depend on a number of geopolitical factors, which I suspect aren’t part of the Farecast algorithm.

I’m wary of predictions, but the fare trend is the key. (FareCompare offes a trendline, too.) If your fare is below that trendline, just buy. Don’t worry about the prediction. If it’s below the average, it’s a good fare.

Related:
- Farecast beta goes public, just in time for a reader review
- So how accurate is Farecast?
- The traveler’s crystal ball
- Market timing: More advice on when to buy cheap plane tickets
- The black art of repricing tickets

Reader Jeff took the site for an extensive spin, and wrote this thorough review of his experience:

Thanks again for the farecast invite. I’ve been meaning to write back to you with my thoughts, as I’ve spent some time looking at their website.

1) The whole thing is a bit pointless, in that they don’t have international travel. Is the gamble of saving ~30 dollars on a domestic flight worth it by waiting a week? I go to Ethiopia once or twice a year, where ticket purchasing can range hundreds of dollars. If I could get a forecast on this ticket price, that could be really
valuable.

2) It appears that their forecast is based on the previous few months of data. They should also be looking at annual sales issues. Reminds me of a Simpsons episode where Homer is bragging to the guys at the bar about what a wise investor he is… he invested in pumpkins, and he said he though they were going to peak in price right around mid November. Flash to the day after halloween and he has lost the family’s savings.

Annual factors? holidays, the summer rush, increase in oil prices over the summer, etc.

3) And finally, we need more than Boston and Seattle. Its great if you live in those places, but if you don’t? The website (which is in beta) indicates this is coming in the future, so it is hard to complain too much.

I did sort of use the site to buy tickets for me and my wife to travel out of Bradley airport, CT, to Columbus next month (Bradley being ~100 cheaper than Logan on average, and we are staying with friends who live 1/2 way between the two airports). I looked up what was predicted for Boston prices for the same time frame (they were going to get cheaper or stay the same), and therefore decided that we could wait on purchasing until we were more sure of our exact travel dates. Turns out we waited a couple of weeks, and the price actually dropped by $15. So it sort of worked.

I think in the end, assuming the service was available for where I lived, I would use it more as a way to predict the urgency in buying tickets- if the price is climbing quickly over the past couple of weeks, act now! But I don’t know if I would be willing to gamble on flight prices dropping if I saw the right flight connections, and a reasonable price.

Twice the website accurately predicted price increases, but twice it missed the boat, once predicting an increase when the fare dropped and once predicting a decrease when the fare went up. On the fifth route, from Boston to Philadelphia, Farecast was fairly close. The website predicted the lowest fare would drop $6 over the next seven days, but it stayed the same.

2 wins, 2 losses, 1 tie.

That’s better than my results. I checked fares for two routes last week: Boston-Chicago (Farecast predicted decline, but the price went up) and Seattle-Chicago (Farecast predicted increase, but the price stayed flat). 0 for 2 for me. Not a huge sample size, admittedly.

Farecast’s excuse? Their software estimates the AVERAGE price over the course of the WHOLE WEEK ahead, not the price exactly one week ahead. Hmm, I see… Well, then they should re-label their “tip” from “wait” to “wait, and check airfares obsessively for the next 7 days.”

P.S. More referrals to the private beta of farecast are available.

I have 25 login invitations to give away. If you want a login to beta-test the site, please use the “contact me” link at the top right of the blog to send me a note. First come, first served.

Remember, the site is in beta, so it only searches fares departing from Boston and Seattle, but you’re welcome to kick the tires.

Farecast goes beyond a cute name. It promises to go a step further than FareCompare’s graphical plotting of the past year’s fares, as reported here last week. Farecast’s goal is to predict the direction fares will go, with a confidence percentage (how confident it is of its prediction) so you can decide whether to buy now or wait.

A neat idea, but it’s clearly not quite ready for primetime yet.

The downsides? 1) So far, the site only includes searches from Boston or Seattle. 2) Southwest fares are excluded, which distorts predictions, since a good Southwest fare sale can send the other airlines into a tizzy. 3) If you see a fare you like, you can’t always book it through the site. You may still need to go to Kayak, Travelocity, Orbitz, or the airline to buy the fare. 4) With current oil prices, and rising fares, it doesn’t take much sophisticated programming to create a site that always suggests buying now.

Farecast isn’t alone in the space either. Coming soon: FlySpy, offering a similar product. I can imagine FareCompare or Kayak adding a prediction function, too. Who will win out in the end? Let me check my crystal ball…