While I very much agree with what's been said above, let's not forget one major drawback of seniority for us pilots: lateral movement in the industry is very difficult indeed... Nothing incenses a pilot's union faster than the words "direct entry captain", for example. although in today's industry, hiring commanders often makes economic and operational sense! Also, once you're out, you're out: I grew up in a seniority system, but after several of the companies I worked for went bust or were restructured, and I chose to go corporate for a while, it's become difficult if not impossible to hope for a job corresponding to my experience and capabilities in a major airline, and the prospect of "starting at the bottom" again becomes less and less attractive. Still, seniority is the only way to go in a big company. The interesting question is: what size should a company have before it's reasonable to install a rigid seniority system?