Blacknight,
I expect you will receive a lot more worthy replies than the one I can offer, but I'll offer it anyway...
When all you move on to line training it is usually in the right hand seat (one would hope) of a 737 or 757/ 767.
Career progression is run on a seniority system, so when for example a command is available training will be offered to the person highest on the seniority list. It has nothing to do with age, but everything to do with the date you join.
I am not sure about changing fleet - but I would imagine the official line is "subject to commercial requirements -"
Again, I hope this is correct, if it isn't I'm sure someone will post a fuller reply!!
Good luck with the final board
