Originally Posted by RealHJ

It's not a benefit, just correct pricing. If the routing is valid and within MPM, theoretically you can have up to 8 SkyTeam airlines on an RT itinerary, as you can have up to 8 flights. The operating carrier of each segment shouldn't matter and hasn't historically mattered, though now as of late it does and for the last two years or so DL is insisting (sometimes, not always) that the route must be published (i.e. available as a through fare, vs. broken fare, on revenue ticket) to be bookable as award. As VS is not ST, if the VS + KL routing is not available for booking via VS or KL, DL may very well say that it can be only additive as it's not published as a through fare by either carrier. That has been an argument used by DL more and more as of late, and why award routing that was available before now no longer being available.