That's awesome, but once you find an itinerary you want, how do you book the flight? Do you usually go to the individual airlines' websites and rebuild the itinerary by hand? Or do you send the 'fare construction' string over to a travel agent?
Depends on the flight, but I usually use a travel agent.
If it's a simple flight, I might use some airline website to book it, but most often for me it's some thing that you can't book at all on the airlines I use. I fly into small rural airports and they simply dot not exist on any major airline's websites.
I give the string to a travel agent and he is able to book the flight no problem.
Thanks. Looks like google flights can do most of it but with gui elements. The one thing it doesn't do which I really like is to be able to specify a layover of 1-2 days, ita does it which is great. (OK I guess I can do it with multi city, but it isn't like the old days where layovers were sometimes a feature not something to be avoided)
To quote myself from a year ago (although Delta and Alaska aren't partners anymore) [3]:
One of the features I like to use a lot is the ability to specify fare classes. As an example, say I want to fly to Tokyo, and I am an Alaska Airlines mileage plan member. Alaska Airlines does not fly to Tokyo, but it has deals with airlines that do. However, sometimes the fare classes are quite complicated. For instance, "Economy" is broken down into many buckets, and not all are created equal. For instance, Delta has at least 13 buckets for Economy, and each 'fare class' awards different amounts of mileage to Alaska flyers [1]:
E: 25% Mileage
L, U, T, X, V: 50% Mileage
H, Q, K: 75%
B, M, S: 100% Mileage
Y: 125% Mileage
If you search on Google Flights, these will all be called "Economy". If you search on most of the other OTA's (Online Travel Agents), you can sometimes find the fare class during checkout or even as part of your search results, but you can't filter on it (Hipmunk is one that does support some of ITA's syntax for these filters, but not all). The buckets aren't always strictly more/less expensive, but they're usually not exposed very easily, if at all[2]. So, you're often left crawling from listing to listing, expanding to see if they are going to get you any miles. (I'll save the debate of whether miles are worth all the effort for another day.)
On ITA, it's not unreasonable to construct a query that says "During the month of November, show me round trips that are between 12 and 19 days that are going from Denver to either Narita or Haneda Airports, which will earn me more than 50% miles on either Delta or American or JAL, but also only ones that connect in Portland or Los Angeles, with no prop planes or overnight stops, and no <50 minute connections or 3+ hour connections". (I wouldn't actually specify all of these stipulations, but they're good for the example! :) )
I also use routing code to force long layover (e.g. go from Europe to SF via London, and spend the night in London to visit friends, on the same ticket).
Theoretically you can still do that with the multi-city search tool on Flights. It should consolidate back down into a single fare if stopovers are permitted.
Aside from what other people have mentioned: I use ITA because it lets me see the fare rules, which helps me anticipate potentially useful mutations to my ticketing. (For example: Knowing that a particular round trip to Paris allowed for a free stopover in London allowed me to attend a conference in the UK for a much lower cost than if I had booked a round trip ticket to the UK.)
