FCR
When you join BA you are given a 5 year “engagement freeze”. BA are not obliged to offer you a move onto another fleet until that initial 5 year period has expired. When you do get a move, say F/O 320 to F/O 777 you then have a 5 year “equipment freeze” applied. You can carry on moving fleets every 5 years if you so wish.
However you can bid to change fleet/go for command etc every year during the month long bidding window (July). BA will offer a “freeze waver” if there is a shortage on a fleet you have bid for that needs filling internally rather than via DEP recruitment.
This year due to various factors a large number of 320 F/Os are being granted moves to long haul fleets inside their initial 5 year freeze.
So clearly there will be a number of 320 vacancies, filled by FPPs and DEPs.
The advice is always “bid for what you want”. Some guys got 320’commands well inside their 5 year engagement freeze as a result. There are always some comedy bids, eg a year 1 cadet pilot bidding for an A380 command - that is streching the maxim somewhat!