"Delta does not allow the instructor to serve also as a seat filler. Not even sure how he could make it work. It would be almost impossible to run the sim panel and sit in the copilot or captains seat. They require a seat filler for a sim with a incomplete crew. If they have tried that with you then you need to call the fleet captain and stop the training. Its not allowed by policy so you will be backed to the hilt."

Not true, depending on the training module, the IP is allowed to serve as a seat filler and perform duties as an instructor. AMF, the IP can do anything up to and including the MV. Cannot perform the LOE though. Generally, DAL recognizes the need for a qualified seat filler.

This is precisely why DAL wants to let the DGS instructors sit as a Seat Filler on a LOE...it cheaper and they're running out of SLI to perform as Seat Fillers. IMHO, some DGS guys have been out of the flying environment for so long, they'd be a serious detriment to a person's checkride.