I began writing a response to your entire post and it was getting way too long.
Before I go off the deep end here, maybe I can get you to consider something. Ok, two things:
#1: Arbitrators and their type (lawyers and judges) look at most things by who got, or who will get financially harmed. You can argue that you deserve Christmas off and your pick of the trips with all the great layovers all you want, but if it isn't costing you any money, they don't care.
#2: With #1 in mind, and you wanting a pay system where all captains get paid captain pay (with longevity) and all first officers get paid first office pay (with longevity), are you not putting in a system where both pilot groups have the same career expectations? (Career expectations to arbitrators means, how much money did you expect to make over your career.)
Are you not putting in a system where both pilot groups are all in the same category and class? (Captain & First Officer pay without aircraft consideration means you have just those two categories, right?)
Are you not putting in a system where longevity is already accounted for? (If a 20 year captain will make more money in his 21st year, and then even more in his 22nd year, no matter what, then as an arbitrator, I don't have to account for him stagnating later on because I put him under someone on the list who has less longevity, right?)
With these things in mind, if we were going to a captain pay and first officer pay system, if we merged with Alaska, Jet Blue, Spirit, or Hawaiian, why wouldn't an arbitrator just put in a straight ratio list from top to bottom? (Actually, for reasons I won't get into, we might even get less than a straight ratio list.)
Geeze. It turned long, anyway. Sorry.
