> The one drawback is sometimes they are missing local / smaller airlines from their list of flights (which can be a major price difference from the major ones) on short flights.
Not to mention they're missing Southwest, but that's Southwest's fault -- they seem to have some sort of policy against allowing any third parties to list their flights. In addition to being really annoying since I have to make two searches rather than one every time I want to book a domestic flight due to a lone holdout, it also makes zero sense to me. How could not having all that free advertising from flight search engines possibly be a good thing for Southwest? I care enough to go to the trouble of searching in two places, but I doubt most people do.
Short Answer: It costs money to be there and they can control the variables and environment better on their website.
Long Answer: It dates back to Southwest's routes in competing with the car for travel. In order to be price competitive, they did not want to pay travel agents a 10% commission. (This was the 1970s) So they sold tickets by the phone, at the airport, or at their office, but always direct.
As computers evolved, travel agents began connecting to an airlines fares by computer, rather than books and a phone. Airlines began developing proprietary systems for managing ticket sales, allowing other airlines to be in their systems for a fee. The biggest were Apollo (United) and Sabre (American). Southwest still refused to pay the distribution costs of the tickets.
When the internet became more broadly available to consumers, Southwest jumped on the opportunity, becoming the first major airline to sell tickets online. Other airline followed and soon after, 3rd party sites came to be, using the GDS' (Global Distribution Systems) like Sabre and Apollo to display all of the flights and fares. Acting like modern day travel agents, and putting many travel agents out of business.
Today, while Southwest has become a much larger airline, it still does not want to pay the GDS' for access to their systems. However, today Southwest has a much stronger brand which can drive more people to their website. And by having the website as the primary channel of distribution, they can control a lot of things that they could not within the confines of a GDS.
It has been debated whether the GDS' are really necessary anymore as middlemen. And besides Southwest, other airlines are trying to bring more people to their controlled distribution channel. In the past few days, Delta and American have removed their flight from several 3rd party websites.
I'd be very surprised if Google Flights wanted Southwest to pay for inclusion. It already lists Southwest flights with a note "Prices are not available for: Southwest. Flights with unknown prices are at the end of the list." Instead it really sounds like it's Southwest not wanting it to be easy for people to comparison shop.
(Disclaimer: I work for Google, on an unrelated project.)
Even then, though, I'd still be very surprised if Google would respond to an offer of seat availability data from Southwest with "sorry, we won't let people search it unless you pay us".
Google works with a few airlines that don't pay them anything. However, Southwest (probably rightly) thinks that if people get used to finding Southwest fares on Google, they'll visit Southwest.com less frequently, increasing Southwest's reliance on Google in the long term. I'm nearly certain Southwest has sent a specific cease and desist to Google to NOT include its fares in results.
Isn't Google sending customers directly to airline websites to book?
So the way this is working is: Google, Hipmunk, etc. use GDS for queries, and then send customer to airline to book? Does GDS have any ability to sell tickets?
Has Google tried to scrape data directly from Southwest website and Southwest won't let them? Or is it just that Southwest will not provide APIs to make it easy for Google to pull the data?
I wonder if it's because people already associate them with being the cheapest, they want people to just default to going to their site and be too lazy to check the comparison sites. If they made it easy to compare, they would lose out on that crowd for any time they weren't the cheapest. Maybe it also allows competitors to beat their prices algorithmically.
Does Southwest selectively offer access to different sites? I know Momondo lists Southwest flights when I search through there. Or is Momondo crawling Southwest's site for prices?
Not to mention they're missing Southwest, but that's Southwest's fault -- they seem to have some sort of policy against allowing any third parties to list their flights. In addition to being really annoying since I have to make two searches rather than one every time I want to book a domestic flight due to a lone holdout, it also makes zero sense to me. How could not having all that free advertising from flight search engines possibly be a good thing for Southwest? I care enough to go to the trouble of searching in two places, but I doubt most people do.