Just curious, but what's a BA 737 doing in JNB? Lost?
If you look closely you'll see it's a ZS registered a/c. Comair operate the BA franchise with domestic and regional services, about 10 rotations a day JNB-CPT, 5 DUR, HRE, VFA, WDH, PLZ and probably a few others I can't think of. They also operate Kulula services sometimes, which is a BA subsidiary too.