DCI is complicated, and it is not consistent across the various feeders. It seems to come down to what your company is willing to negotiate for you.

This is SKW priority (I assume ASA is the same).

Mainline:
S3C by DOH. DL (S3) and DL retirees (S3B) are ahead of us. Not sure if WO's get S3B.


SKW:
S3 by DOH. This puts ahead of mainline and other DCI's, which have S3C.

We also get three S2 upgrades per year on SKW only. This puts you ahead of other SKW empoyees who did not use an S2 upgrade.

I know that 9E does not have as good of an arrangement.