I'm doing a lot of flying these days for international speaking and consulting, and I try whenever possible to have 2 or more clients when I fly overseas, since the trips and time-changes can be draining.

By far my favourite flight search tool is Google flight search. That's because it's an order of magnitude faster than most of the other tools, and while it lacks some features I would like, once you have speed, there is no substitute for it. I also like routehappy when I am being particular about seats, though it doesn't cover all airlines which makes it useless for primary search.

To save money, however, what I really need is a tool that can get smart about the various arcane prices airlines put on flights which can vary tremendously. In particular the situations where airlines have decided not to simply sell one-way fares at around half the price of return trips. This is almost universally true between the USA and Europe and on some domestic routes, and less true on travel involving Asia. It is quite common for one-way trips to cost the same as round trips, and sometimes, bizarrely, even more. In the case of some KLM flights, I have found a one way costing double the price of a round trip. The Dutch know this and commonly book returns on KLM and don't fly the return leg. There are stories of airlines punishing people who do that but they are rare. (The airlines are much more upset about "hidden city" booking, where people notice a flight to X connecting through Y is much cheaper than the direct flight to Y, so they book to X and just walk off the plane there.)

Throwing away the return leg doesn't stop the trip from costing as much as a return. Your goal is to pay a more fair price, and that usually means making sure that you fly all your flights (or certainly your transatlantic flights) ticketed by the same airline. That works some of the time, but not always. The best airline to fly out may be a terrible airline to fly back on. You may have to take a flight with a painful time and routing one way to get the schedule you need the other way. Of course, this is the supposed purpose of the pricing -- to make you buy both directions from the same airline, but it's often a false victory, I suspect it loses for the airline almost as much as it wins, and it pisses off customers.

Trying all the permutations

Airlines have tons of hidden fare rules that jack up or seriously reduce fares involving certain cities. If you are going to these cities, you want to use them.

If we consider a complex trip that goes A -> B -> C -> D -> E -> A (4 stops) you can put that into most of the flight search engines as a "multi city" trip. You'll sometimes get back a great answer, but usually you get back a ridiculous one. That's because the engine just shops that out to all the airlines, which means you only get airlines that sell all 5 routes. And if the itinerary is far flung, there may be no airlines that sell them all at a good price, or with a good routing. (Of course, rarely does any one airline fly all the routes, but they all have tons of partners they can build tickets from.)

So it turns out the best way to fly this trip means combining one-ways (where they are fairly priced) and open jaws. I have found, for example, that you can often save a huge amount of money by buying something like "A->B, D-E" from one airline and "B->C, E-A" from another and "C->D" one way from a third. Bizarrely, adding the right extra legs to certain itineraries triggers serious price drops. This is particularly true when you involve cities with lots of competition (like New York) or inherently low prices (like India.)

So what I want is a flight search engine that will try all the combinations. There are engines that will check if sets of one-ways will do the trick (Kayak calls it a hacker fare) but that's not enough. Price all 5 together, and then the sets of 4 with a single one-way, then the sets of 3 with the different sets of 2 and so on. You want to combine the price search with a flight quality search too, so that you flight on shorter, better flights.

When I do this as a human, I do it with some knowledge of the geography. For example, if you have a short leg which is only flown nonstop by one airline, it's pretty obvious you want to price that out independently from the other flights, because if your ticket comes from an airline that doesn't partner with the nonstop airline, they will put you on a ridiculous connection instead of a cheap one-hour flight.

In addition, there is another advantage to breaking up a flight into smaller groupings. It gives you more ability to change the flights or even to skip them. In many cases, to avoid people playing tricks, airlines will cancel the rest of an itinerary if you don't show up for an early leg, often with no refund. Once, when a change in plans put me in Copenhagen instead of Bergen, Norway the night before my planned flight from Bergen back to San Francisco (via Copenhagen), SAS insisted I fly to Bergen just so I could turn around and get on the flight back to Copenhagen for my connection.

Round the world

This gets worse when you do a multi-leg trip, and worse, a "round the world" trip involving Asia, Europe and the Americas. In the latter case, sometimes your best course is the special around-the-world tickets offered by the 3 big alliances. These tickets cost around $10,000 in business class, around $4K in coach. For certain types of trips they are the clear winning choice. They are flexible -- you can book them as little as 3 days in advance, and you can change your flights, even the cities, for free or low cost. They are refundable with a small penalty! You can add side trips for personal travel at little to no extra cost, and you can go to obscure airports that are expensive to fly to for the same price. They have a small number of downsides:

• They can cost more than many directly booked trips. If your client is paying, it may not be fair to charge them $10K for something you could book for $7K. Though you can always eat the extra cost if you are doing side-trips as it can easily be worth it.
• You are limited to one alliance only, though most of them have several airlines to fly you on the route.
• They fetch from a more limited inventory if flying in business class, so quite often, particularly if booking late or changing your plans, you may see the flight you want is not available in the class you paid for.
• Of course, they have their RTW restrictions -- you must cross each ocean exactly once, along with a few others. Usually not a problem, but sometimes.

So if you ever see that your complex trip is adding up to a high cost, look into these. OneWorld also has some subset trips that don't require a Pacific crossing.

Smart travel agents

While a computer should be able to do all this, perhaps there are still members of the dying profession of travel agents who can do a decent job on this. Let me know if you know of some. In the past, there were ticket consolidators, who buy up buckets of tickets and then have the power to sell them at reasonable one-way prices. This can be good, though sometimes it means being a 2nd class passenger, not getting loyalty miles and not being able to deal directly with the airline for service.