|JNB-IAH First flight cover, December 1982. Source: The Timetablist|
It's unclear to me exactly what market this peculiar route was intended to serve, especially since Houston was nothing like the international air hub that it is today (in 1982, the only other trans-oceanic flights out of IAH were to London, Paris and Amsterdam) and Apartheid-era South Africa was not exactly a major travel destination. Was it intended to be an energy-related connection, even though South Africa was not a significant petroleum producer?
Needless to say, the presence of the racist government's airline in Houston was controversial, and local civil rights activists successfully lobbied mayor Kathy Whitmire and city council to revoke SAA's landing rights even before Congress passed the Comprehensive Anti-Apartheid Act of 1986, which barred South African airlines from flying to the United States.
SAA did not resume the service after Apartheid ended and the ban on its flights was lifted. Scheduled air services from Houston to the African continent would not reappear until 2011, when United began nonstop flights to Lagos, Nigeria.
Flights from Houston to South Africa would make much more sense now than they did in the early 1980s, considering how much larger of an international travel hub Bush Intercontinental is today and given that United and South African Airways are both Star Alliance members. During a trade mission in January of 2014, mayor Annise Parker and city officials even discussed the matter with South African aviation officials. It's possible that flights from Houston to Johannesburg could someday again become a reality. The longer ranges of the Boeing 777 and 787 mean that interim stopovers in Cape Verde are no longer necessary.