There are many airlines that are offering flights to South Africa arriving at any of the three international airports, which is Cape Town, Durban and OR Tambo International Airport which is in Johannesburg. You will find that most flights that are destined for either Durban or Cape Town will pass through Johannesburg anyway.
It is quite possible to get rates that are discounted if you are going to be traveling to Johannesburg between the months of June and December. This because during the first part of the year; the place has a high number of visitors trying to avoid the rains during the winter season. Travelling during the week days instead of over weekends will also get you lower air fares.
There are a number of places on the internet where you can get information regarding flights to South Africa. There are agencies that will be able to take care of your flight arrangements and other holiday requirements if you need them to. If you can order your ticket online then you will be quoted a lower air fare and making an early booking will no doubt get you a reduction in the air fares too. Basically making a booking two weeks in advance of your departure date qualifies to be called an advance booking.
Considering the flights to South Africa you have direct flights and connect flights. If there is no real emergency then there is no need for you to fly direct because it costs more. If you compare the arrival times of the direct and connecting flights its normally less than three hours.
The Air fares also vary according to the time of the year that it is. So it is not possible to get any fixed rates at any one time, estimates might be available at any one of the following:
