I think the only seniority people are talking about is being unable to retain your current rank when moving jobs, I think everyone would agree that any in house promotion should (but it's not a perfect world) be done on DOJ (seniority) and suitability i.e. have the minimum qualifications. Also 7Q off, direct entry Command positions still require minimum qualifications (often greater than in house requirements), A/C type experience so on and so forth, so don't expect to walk into a 747 Command with a Major carrier with $$$.