EK with AS miles or QR with AA miles will be your two best bets for MLE and SEZ (EY is of course a good option but requires two awards as noted above if redeeming AA miles - but you only need one award if using QR - QR and transiting DOH to get to Africa which makes it a great option for AA redemptions to Africa - you'll need to search for space using BA Avios website, QR space doesn't show on AA website).
EK is of course EK but they jacked up the redemption rates so it'll cost a pretty penny to redeem AS miles for EK J or F these days (if Y, I don't think the pricing has changed).
DL there are a few threads that can help you but MLE is definitely doable, I believe AF just announced a new CDG - MLE flight which will help for SkyTeam award availability to MLE. There are some nuances (search the DL forum) around having to search segment by segment and I'm not sure if you are allowed to go East to get to MLE but if you are, KE is a good option for Y and J (and of course you can combine with a DL flight to ICN to start).
Another thought, if you want to leave Africa from JNB, I would recommend using your AS for a CX J redemption (assuming you are looking for J, if not Y works too) and go JNB - HKG - BOS (based on your profile saying VT). You can add a free stopover at HKG too if you want - it's one of the best values still out there (only 62.5k/person).
To me the ideal booking would be (again assuming BOS being first choice due to VT):
BOS - DOH - SEZ / MLE (AA award redemption on QR)
SEZ / MLE - JNB (paid flight or potentially UA award on SAA)
JNB - HKG (potential stopover if you have time) - BOS (AS award redemption on CX)
Or the reverse.
The above would be:
150k AA (75k x2 for J)
60k UA (30k x2 for J) or cash (or someone might have other ideas for better award redemptions intra-Africa)
115k AS (62.5k x2 for J)
Last edited by Duke787; Apr 23, 2017 at 10:44 pm