Originally Posted by
southpaw1227
The problem seems to be that said flight is operated by PenAir, and Delta's Diamond line is telling me that they can only use SkyMiles redemptions on AS flights operated by AS or Horizon, and *not* PenAir.
Pen-Air is not DL award-eligible. It's the common partner-of-a-partner problem. AS miles can be used for Pen-Air flights.