There are really only two outcomes for how a SLI proceeds. One is a pre nuptial agreement. It’s done as a condition of the merger proceeding. Generally however this only happens when management and the pilots at the purchasing airline have a good relationship because it gives the acquiring airlines pilots the ability to veto the merger. Prenups are very rare with the last one probably being SWA and Frontier. No agreement was reached and the merger was cancelled.
The other is managements announce the merger with no conditions on SLI integration. ALPA merger policy Governs the process. A negotiated settlement is attempted and when that fails as it almost always does it proceeds to binding arbitration. The arbitrator is supposed to use ALPA merger policy as a guideline.

• Career Expectations: Preserving the professional trajectory pilots expected at their pre-merger airline.
• Longevity: Length of service with the respective airline.
• Status and Category: Current rank (e.g., Captain vs. First Officer) and aircraft type.
• Internal Relative Seniority: A pilot's position relative to others at their own original airline cannot be changed.