I recommend using US Airways. You can transfer mile for mile into US Airways from AMEX, and since US Air is *A you can use those miles to book on South African. One particularly nice thing about this option is that you can call US Air to check availability and once they confirm that a seat is available you can do the transfer online while you are still on the phone with them and the AMEX miles transfer immediately, while you wait! So, you never have to get stuck in the trap of transferring the miles only to discover that the seats you wanted are gone by the time the transfer is complete. I should note, by the way, that I have not done this transfer in a while--but it is likely that the instant transfer still works.

To other FT readers--has anyone done this ransfer lately?