Key aspect is looking at the flight numbers and who’s code it is DLxxx vs VSxxx vs KLxxx vs AFxxx and operating carrier just needs to be skyteam or partner

i always check https://www.delta.com/us/en/skymiles...rline-partners

cheap Z fares is often best for partner coded, especially for the longer distances. PE is true too though upgrades on Delta operated domestic don’t go through on partner coded flights until the 24 hour mark