When does United release various booking classes?
 

Is there a rule of thumb when the different classes are released?

I'm looking to book a trip to Australia for next year. So far for the dates that I want to go, the lowest outabound available is T class and the lowest inbound is W class. The flights are 10 (or 11) month away. For the ones that are 11 months away the tickets have not been released yet.
I would like to pick up L, K, G, N since they would probably be cheaper.

Thanks!

Are you looking for the release of the booking class or an eligible fare?

I suppose it doesn't matter, there's no publicly available schedule for either.

Although far out tends to start with all inventory classes opened up, as cheaper fares are sold, the lower fare classes are zero'ed. As time goes on, UA may re-open the lower fare classes.

There is more to pricing than just fare classes.

There also needs to be a fare rule filed for the fare class with a price. It is not unknown for UA to never file a fare rule for the lowest fare classes --- especially G & N.

Additionally a fare rule for a K fare at 10 months out will not be the same price as a K fare at 1 month out. So you may be able to get a K fare later that is more expensive then a T or S fare today.

It can happen any day at any time.