The difference between "Sold out" and "Unavailable"?
 

I often see some tickets are unavailable even for far away dates. What's the difference between "Sold out" and "Unavailable"?

I've always believed "sold out" = the plane (and its overbooking component) is physically ticketed while "unavailable" = we don't feel like selling you a ticket at the price you want, buy AT or BS instead.

WGA fares sometimes have cut of dates or capacity availability...at which time the fare is "unavailable". Term also applies to flight that are not bookable past or close to the departure time.

Sold out is just that...no more seats on the plane. I do not think they use they term "sold out" on say WGA fares when Anytime and BS fares are still available.

I just looked at a few dates. I found some flights with "Sold Out" across all fares. Some with "Unavailable" across all fares. Some with "Unavailiable" for WGA only. I found a few with WGA "Sold Out" and AT AND BS fares posted and one with BS "Sold Out", WGA "Unavailible" but AT fates available.

Someone posted a while ago that "Unavailible" may mean that some seats are being with held for Southwest Vacations and it was sometimes possible to purchase them through Southwest Vacations.

There are a lot of reasons why they might not want to sell you a particular ticket on a particular flight at this moment. It seems like all of those possibilities are lumped together under "unavailable" except the case where the flight is physically at capacity, which is shown as "sold out".

Or through a third party like Apple or Funjet? Could even be smaller local travel agency that has blocked a bunch of seats for a tour that might be returned at short notice.