Originally Posted by
3Cforme
1. One can not combine classes of srvice between origin and destination.
...unless ONE is Delta.

Say you're flying AAA-BBB-CCC, where AAA-BBB is a domestic flight and CCC is int'l destination. I've seen itins at DL.com where the domestic segment is in Y, the int'l segment is in C and they charge the biz rate. (nwa.com used to do this as well).