It might be worth adding that it isn't only rostering that is important in respect of seniority. It is also vital to ensure fair allocation of fleet positions. Our reluctance to insist on strict seniority results in a lottery of type allocation, whereup senior people risk being trapped on the worst fleets (and in fact are). Or do you think it fair that a jr Captain is entitled to a slot on the 777/350 and a much senior Captain is trapped on the freighter, with no ability to ensure movement to the better fleets during their career? With our current system, anyone is subject to arbitrary and capricious disadvantage, which can affect your entire career. There is a downside to strict seniority (the early years are more difficult), but it is truly the ONLY system that ensures fairness overall. As ATY said above, if you haven't worked in such a system, then accept you really don't know what you are talking about.