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Comment by mepiethree | Hacker News Reader

Wow, I am very different than those users. I just think "how fucking hard can it be to show me the same flight prices you showed me 30 seconds ago," and then switch to Google Flights

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As I recall there are (or at least used to be) lots of computationally hard problems in searching for flights. I think it is already somewhat tricky to enumerate all the reasonable routes between two destinations (and back) (and sometimes there are C shaped plans of A->B, then days later B-> C), and then airlines have complex fee structures combining date, time, class (ie fare), loyalty programme memberships, legs, whole route, current demand, etc such that determining the price for a single route is somewhat tricky and searching for the fastest /cheapest route is also not easy (and crucially not reducible: if you have the cheapest flight from A to B, the cheapest return from A to B may not include it)

But maybe the landscape of airline booking/pricing has changed since I got this impression.

I imagine a big part is just having to talk to the airlines legacy systems. If Skyscanner (et al) had access to all the data, I expect they could compute prices quicker and give better options. I assume this is why Google bought ITA Software.

I've got first hand experience in this as we are working on it right now.

This problem is largely due to the closed and archaic nature of the GDS systems that are the source of truth. These systems have been running for 40+ years and no one wants to touch them to make substantive changes. As a result, modernisation is attempted via layers on top of layers that just add complexity confusion.

There is a difficult routing and fare calculation problem here, coupled with a distributed consensus problem. While better solutions to this exist or may exist, the biggest hurdles are the organisational ones.

Why is the routing and fare calculation a big problem? I can see writing to a legacy system being slow, but I would think there could be constant caching somewhere of the data as it is read by anyone, and thus reads could be mostly fast, making routing calculation fast. Then it would be a matter of checking for validity of chosen routes.

I worked at a GDS and you're pretty close. There's a component of not wanting to change, but when they do they are burdened by their fragile infrastructure and thousands of competing projects. Very small changes would cause defects in one project that one customer uses. While massive bugs are ignored.

> and then switch to Google Flights

Which will most likely show non-bookable outdated prices more often... there's always a trade-off. There might also be some browser/geo profiling going on.

> Which will most likely show non-bookable outdated prices more often

Why do you assert that?

Certainly because they have to cache results to load the results as fast as they do.

They don't cache them this way.

However, I'm not sure they really changed the engine underneath, and it was always designed as something that then was input to booking sites, often with filters on fares, because QPX (the engine) would show you fares that an agent with full view of GDSes would see - and sometimes the airlines don't want to sell certain fares (it already filtered the special unsellable ones of course, but it couldn't apply arbitrary policy decisions from airlines).

Not the OP, but I have personal experience with Google Flights showing non-bookable fares much more often than I’d like/expect.

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