Originally Posted by
akonradi
Just like revenue fares, you must reissue the entire ticket. Low inventory may not become available immediately after you cancel the original ticket, and the reissue will price higher if this is the case. Your best bet is to wait it out to see if you can find any MSP-LHR itinerary with low pricing, then reissue the whole thing (assuming that AF still has O available).
Hmm, I'm in the midst of booking an award ticket right now, and asked a SkyMiles agent almost the identical question just yesterday. Her answer was exactly the opposite. I could change the return after ticketing without affecting the outbound.