Originally Posted by
B747-437B
There is only one international terminal in Johannesburg. The only reason they have the silly "A" and "B" designation is because SAA check-in counters are located between international and domestic security entrances (hence called "B"), which is separate from the other international carriers who check-in at "A". All flights actually arrive and depart in the same place however.
Most/All *A carriers actually use the B check-in desks (or used to, MS definitely does)