Although a plethora of travel search engines try to dazzle you with options, planning your next trip could take far longer than you expect. Here are some common truths about search engines that are often overlooked.

Nearly All Will “Time out” and Overlook Some Options

The number of possible ways to get from point A to point B using modern air travel is simply staggering. While search engines usually bring back more results than you can shake a stick at, they don’t actually find every route possible. Even if a single route is considered, there may be hundreds of fares or combinations of fares that can be used to book what otherwise appears to be the same trip. The branching factor is simply too big to search every itinerary and get back to you with an answer in a reasonable amount of time.

The best itinerary may never show up.

To avoid this concern, make sure your search parameters are sufficiently constrained. Don’t let it search dates or carriers you have no intention on using. Scott has some examples of how to narrow your search using ITA Matrix and avoid dreaded error messages.

For heavily trafficked routes between two major airports, like New York-JFK and London-Heathrow, one of the easiest tips is to narrow the departure time window (otherwise many tools may not show you flights later in the day).

Search Engines Are Biased to Funnel Traffic through Hub Airports

Get to know how to use Wikipedia airport pages to see if there are still logical connections the websites are missing (LAS, non-hub connections, LAX, SEA) — or use these tools I’ve built here tracking all routes between North America and other continents. You’ll be surprised at some of the “hidden” routes airlines fly from non-hub cities.

Most Tools Will Assume You Prefer the Cheapest Fare

We all like to save money, but some tradeoffs are acceptable. Do you really prefer to save $10 vs. itineraries that keep you on the same carrier? Likewise, most tools will assume you’ll choose itineraries that have ridiculous airport transfers or absurdly long layovers just to save a few extra bucks. (Hopefully you won’t have to use the money you save for an overnight layover.)

Luton is much further than Heathrow from the center of London.

Finally, beware of secondary airports frequented by low-cost carriers. It may say London or Brussels, but that long, expensive ride into town is going to negate any savings you would have achieved.

With any results, check closely for airport changes, long layovers, and airports extremely far from town. Assume that switching carriers will compound difficulties with check-in, re-issuing tickets, and checking bags — problems that can be almost as great as if you booked two separate tickets.

Results Rarely Provide Indicators of Quality

Airlines don’t market their flights or draw any distinction between massive variations in quality amongst their own fleets and their partners. Wi-Fi and flat bed seats vs. 28″ pitch and projector screens at the front of the cabin? It’s all the same! Basic symbols for on-board entertainment or meals could still vary widely in practice depending on the route and aircraft type.

Results from Routehappy will show you different amenities and use that information to give each option a happiness score.

While a few services like Routehappy and Hipmunk and making great inroads into helping customers make decisions based on the relative comfort of a flight and carrier, most engines will leave you blind. Develop a sense for which airlines are better than others by reading reviews and using services like SeatGuru and reading other traveler’s reviews on blogs and forums. For example, it’s helpful to know Etihad is going to give you a better experience than Air Berlin on most itineraries.

Also take notice when you’re flying a domestic U.S. carrier whether you’ll be on its mainline service or its regional airline counterpart. (The latter have planes with a far lower tolerance for inclement weather and delay/cancel far more frequently.)

Understand your deal breakers so you don’t set yourself up for dashed expectations or a miserable flight. In my case, I know I can handle 31” seat pitch but would be absurdly uncomfortable in 28” seats. It’s not worth even $100 in savings for that tradeoff.

Many Websites Are Designed to Upsell

Search engines and online travel agencies (OTAs) make the most money on ancillary referrals to hotels, car rentals, and other travel service providers like insurance companies — not the actual flight booking. (Airline commissions are so low that they account for single digit shares of OTA gross margins.) Booking sites will do everything they can to get you to add them into a trip.

Keep that incentive in mind as you soldier though the onslaught of upsells. Remember that most 3rd party bookings will be the first to be shown the door when operations go sideways.

Conclusion

There is no right answer when using these tools since everyone has different preferences for flights. But if possible, try to follow these guidelines:

• Factor in the cost of your time. Many of the decisions above become a no brainer when you factor in that an hour of your time is worth something greater than zero.

• Do your research. Go into a search knowing what the options are. The more you research, the more you’ll be able to read between the lines of the results that come back.

• Book with the carrier directly. All else being equal, book with the airline direction and try to fly the same airline through a hub or at least an alliance partner. Especially for longer trips, simplicity is key.

I hope this rundown of common search engine misconceptions will help you in the search for your next vacation. Have a tip or strategy you use? Post it in the comments below!