Conversely, management doesn't like the seniority system because as pilots get older, and presumably more senior, they start to cost more, with sick time, more vacation, higher rates each year via longevity, etc.
This is true in non-union shops as well.
HalinTexas is correct the seniority system essentially makes workers into indentured servants. I am a management professional that earns equivalent to a captain at the better paying airlines. Not only do I have the option of going to work for a different company should my company disintegrate but I regularly get solicited for positions with competing companies. Both options are available to me generally with same or better benefits. I have been in my current position for about 3yrs; I get 6 weeks of vacation as an example.
In a non-union environment the company negotiates with each worker. When you are talking about specialty skilled positions the employee almost always has the upper hand. Companies spend a lot of money, time, and effort in ensuring top performers stay and grow in the organization. If a company isn't the most competitive company out there for the work force then its workforce shifts to the competition. Companies also work aggressively to shed poor performers out of the organization.
Many here will say people are unfairly targeted and fired by management when it comes to the poor performer topic. That maybe true in some cases but in 90% of the cases people get fired because they are anti-social, unproductive, and unintelligent miscreants. About 30% of this forum couldn't hold work at McDonald's which is why we have unions, so the 70% can protect the 30% who in prehistoric times would have been thrown off a cliff at birth. It is also always important to note that the 30% will always end up in union leadership positions; not the 70%.
When I managed in union environments it was actually a bit easier. The quality of the work force is roughly equal. The union work force does provide greater stability as the seniority number means you don't have people leaving because they cannot get like paying positions. It is key to ensure you hire the right people because it can be hard to fire union workers. In terms of pay negotiations it was always better/easier then non-union following two simple steps.
One make the union think you are going to scorch the earth which after enough time they always begin to believe. When you have 30yrs invested and can potentially lose everything even a little seed of doubt grows like wild fire.
Two once everyone was sufficiently freaked out you offer the existing work force a small bone in exchange for a B scales and work rule changes for any new hires. Union work forces are about the most self centered groups (see discussion on national seniority list) so the concept of get for me and screw those who come next is a natural thought. When coupled with the bone of a 2% pay raise which when you consider the work force was so freaked they were going to get locked out six weeks ago they are now doing cart wheels and gladly sign the deal. Union leadership is quick to point out that 2% is better then anyone else would get. Of course during same time the non-union office staff was getting 5-30% bonuses and 3-10% base pay increases.
This is how you lose scope, work rules, etc. This works out great for the company as we tend to negotiate over decades to improve the bottom line but unions negotiate over short term contracts. Quite honestly unions have become the best and quickest way to get savings out of an organization. You see it repeated here in every negotiation thread:
1.) Company and union get into death spiral of negotations
2.) 30yr Captain realizes he could be flying a CRJ for $15K a year
3.) Company offers $1.00 raise and 2 bags of peanuts every flight to crew in exchange for 50% wage cut to new hires and outsourcing of any plane under 250 seats.
4.) 30yr Captain gladly signs on the dotted line and ensures he always stores 1 bag of the peanuts under a tree to save in case age 70 doesn't pass.
The only thing that makes this possible is a seniority list which binds you to an organization (indentured servant). You think Microsoft, Google, IBM, etc. could as easily slash costs out of their entire work force? Somebody told a programmer at Google all he was getting was a bag of peanuts he would be out the door for Microsoft or the next hot start up in thirty seconds or less.