I guess I'm looking for the definitive rule on the OP's question. If you are booked on flights with non-DL ST flight numbers (KL or AF for examples) but your itinerary includes a US domestic leg on DL metal, are you eligible for an upgrade on that domestic leg? Yes the OP said the itinerary read not eligible, but it's not clear if that's an IT glitch that fell through the cracks and can be rectified at the airport or by calling the medallion line or if it is a set rule.