Seniority COULD be brought with you, but different airlines calculate it differently. The TWA debacle is a case in point. Company seniority? Occupational seniority?
And what about retirement? Each airline has a different plan. If and when the airlines eliminate the defined benefit plans and substitute a defined contribution plan, it could be a bit more workable.
AMFA is a proponent of industry seniority, but i wonder how they define it. At some airlines, mechs waltz back and forth between aircraft, automotive and plant maintenance. At others, they are separate.
And some rampers/fuelers have dual occupational seniority, some have previous in bldg cleaners, etc, etc.
A Pandora's box indeed.