Southwest periodically make flights for further in the future available. The schedule was supposed to be extended on August 16th, but that was pushed back and the schedule was actually extended yesterday. You can now book flights until April 7, 2019. On September  27, 2018 the schedule will be extended again for flights until June 8, 2019. There was some hope that the schedule being extended was put off so that Hawaii flights would be bookable, but that’s obviously not the case.
Southwest has a pretty good cancellation/refunds policy, depending on the fare you’ve booked you’ll either receive a credit towards a future flight(Wanna Get Away) or cash refund (Business Select or Anytime – returned to credit card if you used one). That means it’s often best to book flights as soon as they become available and periodically check to see if the price has decreased, if it has you can click ‘change flight’.
I don’t undestand why they’re the only airline that doesnt show up in search flight websites like Kayak and Momondo.
Because presumably when an airline fare is sold through a site like that, a cut of the flight is paid to the website that the user purchases on, and southwest wants to sell their own flights to make 100% of the money.
+1. They also do it to force people to do a search on their site to compare, they are hoping to not only compete on price when that is done (e.g well I could just pay $20 more for this more convenient flight)
They don’t want to pay the commission fees for third party bookings.
Now waiting for the next release.
There website has always shown accurate information for me, although it is changes from time to time. Within a couple weeks it is usually locked in though:
https://www.southwest.com/air/flight-schedules/
“We are currently accepting air reservations through April 7, 2019. On September 27, 2018 we will open our schedule for sale through June 8, 2019. This date is subject to change! Please check back frequently.”
Interesting, I was on the phone with customer service yesterday and they told me the next extension to June 8 would not be until November 15.
Yesterday i was looking for a cheap fly to AZ for spring training 2019 and saw this, i was able to get 3 round trip tickets for 10k points each, its great to have the opportunity to book in advance.