IMHO scope should be based on Certificates. Delta pilots perform Delta flying. Pilots performing Delta flying are a part of the same craft and class of worker.

Next, if that is not obtainable, is scope based on type certificates.

Payload and even MTOW can be changed with a log entry and a sticker. Republic would change the GTOW on an overnight depending on which airline they were flying for (American (aka US Air) allowed more than anyone else).

Honestly, back when some of these provisions were designed they were not well thought out. None the less, that is what we have today and the provisions have been sort of grandfathered forward. The E170 is a "scope buster" and we should have stopped outsourcing at the CL-65. While they are all "mainline" jets, the E175 only gets to 86,000 via a "certificate of convenience."

I had hopes an airline would engage in a grand redesign of outsourcing with the end state goal of insourcing. The economics work.

Delta is headed that direction. It is a bit of shame that management is being unreasonable about PS, pay, vacation and other marginal items that are standing in the way of a new agreement.