Different unions all work differently.
For instance Seafarers work on a first in first out type of system that I believe you can decline assignment as your name moves up the list at the union hall, to try and get better choices of ship, destination, etc..
But if you are a cook you will not get an engineer assignment, just as the engineer will not get a bridge assignment, does not matter who has been a Seafarer longer. So I guess Seafarers are "special" too.
I do not know how Police and Firefighters work, but I am pretty certain it does not matter who was hired first, but who passed the test and training to move up and become Inspector, Captain, Chief, etc.and when the city has to layoff it may not necessarily go DOH.....So I guess police and firefighters are "special" too.
Teachers....I would think pretty similar to Police and Firefighters...extra "special" too..
We all deserve better treatment. That is why we form unions, but pilots form associations, because they have circumstances that are different from other labor groups.