...Seniority allowed you to know where you stood in terms of
last on first off, route bidding, equipment and promotion. It
eliminated any brown-nosing of the higher ups - you got the
chance of promotion or equipment upgrade when it was your
turn. Screw it up and you went back to where you were last at.
Leave and a few other items were also dependent on this
system to keep the peace and brown-nosers out of the works.
Same worked after promotion - a senior FO went from being
king of the ****s to **** of the kings with Reserve blocks etc.
But it all worked and we all got on well. The ruination of this
system, as well as the global airline industry in general began
in 1985 in the US. Look it up.