Fairness is NOT an objective standard, period.
It is the only standard, hence the purpose of grievances and arbitration.
Seniority is the one Objective standard. If they entered the industry ten years before you, you wait.
Seniority has NEVER been about who entered the industry first. I'm junior to others who began flying or entered the industry long after me. Entirely irrelevant.
Seniority is based on date of hire at a particular company; something not necessarily relevant when two individual companies are merged. After all, I don't care who was hired on what date over at brand X; it doesn't affect me in any way, shape or form.
Unless, of course, they're going bankrupt, we save them, and then someone over there wants my job based on the date he was hired...at another company.
That's why the matter was arbitrated in the first place...and why it was decided by an expert arbitrator who had dealt with many airline mergers, that relative seniority was important if not more so than date of hire.
Seniority at my own place of hire is based on date of hire with this employer...nobody here could give a stuff about my date of hire with any former employer. During a merger then, nobody cares who was hired when with a former employer. The merger is an entirely new show, and an equitable (yes, fair) means of merging the seniority lists must be found. Date of hire with a former operator is not the only way, or even the most appropriate way, to do this.