when they EVENTUALLY "diverted", they went to Langebaan... and had to tell ATC it is a 'crisis'. Fuel planning a bit lacking?
It was a 319, presume it was from Durban, his alternate would have been George or PE, probably George, SAA uses SITA flight plans, fuel for contingency, alternate etc is acurate to 10kg.
Langebaan is not the normal alternate so no he should not have gone there, the reason they probably did was they took a chance that the airport would open went into there alternate fuel for George and changed there alternate to Langebaan probably had permission from Ops at that stage as it does make better operational sense. when he got to Alternate fuel for Langebaan it was probably close to 45min left in tanks and according to SAA Operations that is a mandatory urgency call (30 mins is mayday) hence you say it was a crisis, not really a crisis just that Ops manual state it must be brought to ATC attention as a urgency call.
Let me assure you SAA fuel planning involves SITA flight plans and state of the art aircraft and training, management at SAA (like the rest of the world) wants the crew to take SITA fuel to cut down on the cost of tankering fuel all over the place, thats fine until you have a small problem like in CT and then there was no holding fuel.........most Captains will add a small amount of extra fuel on top of SITA fuel but some dont (as per management wishes).
Hope this answers your question