Just explaining the "why."

There are two ways to get to a merger. First, is when an airline's management wants a merger for their business. Second, when the workers force the matter.

In the second case, at Delta, the Delta Pilot Working Agreement with management stipuates that if the Company acquires an airline which operates aircraft above the limit of permitted aircraft (over 76 seats) then management has agreed to a merger.

The other way to force a merger would be to ask the National Mediation Board to find that the acquired carrier is part of a single transportation system and that the employees are part of the same craft and class for representation. The reason why Compass was unceremoniously kicked out of the Delta representational structure was to help define those small jet pilots outside of the "craft and class" of Delta pilots. ALPA has worked to define permitted flying as no longer Delta flying, performed by Delta pilots, so as to avoid a merger.