You may be able to apply a SkyTeam Upgrade (if your current ticket is in Y/B/M class).
@
KVS Thanks for the tip about applying a SkyTeam Upgrade on this (JNB-CDG) segment. I called Delta Skymiles and asked if I could use Delta miles for an upgrade I booked on AF on the AF website. Delta told me I could do this with a SkyTeam upgrade and they charged me 35K miles for the SkyTeam upgrade. Much less than I thought it would be. Again, thank you for the guidance.