Mig 21
There were no Mig 21 aircraft in the ZAF inventory at that time. Mig 19, Galeb, Jastreb, and MB 326 were fighter aircraft on the ground that day.
There were no aircraft in quick reaction positions to respond to the well executed attack, and positioning of CAP aircraft overhead Mumbwa. They were totally surprised and ill prepared.
I was hoping those guys would make a move down there, but fortunately for them, and the ZAF, they did not.