I was ridiculed and laughed at for suggesting AS/VX would have gone 50-65% longevity and 50-35% stat cat respectively. Arbitration made it 60% longevity, 40% stat cat. If you were honest with the vast differences between the two carriers, the uber disparity in longevity, and the CBA that AS brought to VX, it was clear AS was going to be favored a lot more so and that would be via longevity.
There is virtually no difference between Spirit and Frontier going forward. Frontier may hit the quick upgrade spurt that Spirit had a few years ago from 2014-2016. Spirit/Frontier would almost certainly be a 15-25% longevity, 85-75% stat cat (respectively) with no fences in binding arbitration. Frontier started 1994, but small number of pilots overall until now. Spirit 1983 but the overwhelming majority of pilots have been hired post 2010. It would be an easy/no brainer integration. No fences. No major airline integration of the past 20 yrs has put fences on narrowbody equipment. NK/F9 wouldn't either. Pinnacle/Colgan/Mesaba was a fluke just like the Republic/Lynx/MidEx/Frontier list a while back. Regional SLIs end up being different, especially given that arbitrators see them as stepping stone airlines so career expectations are vastly different between those and a career destination (major airline).