To fly SYD-JNB, Virgin will have to fly via / over Perth, then to Mauritius until they get within Etops range of FIMP before they can turn South to JNB. Whether they can make it one sector SYD-JNB that route, I'm not sure.
Even though it is a lot longer than the direct track, if they go via Perth, they could also tap into the South African / Rhodesian population living there, and anyway, the lower operating costs of the 777 will go a long way to offset the extra route distance.
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