We have this thing called "Vacancy bids". It comes out a few times a year so people can bid out of their current seat or base. The current active bid is 2306V. It opened on the 3rd of FEB and will close on the 14th of FEB. During this 12 day window all pilots can submit their transfer preferences and the computer will process them in seniority order. 2306V means the year of 2023 with an activation month of 06 and it's a Vacancy bid. So if you got a base transfer award during this bid, you can expect the transfer to take place in June. The last bid 2305V took place in late December and will activate this May. If you are in training and 230xV comes out during that time, you are eligible to bid another equipment/base or both.

Timing is important, if there's a vacancy bid after your initial newhire bid, you can bid again right away and potentially be awarded another base/equipment during training.

There are exceptions but yes.

Some class drops have only a handful of 737 Vacancies, you never know until the morning of your class drop, don't count on it.