Johannesburg - The OR Tambo International Airport, outside Johannesburg, was experiencing flight delays on Thursday due to a power outage, it said.
"While essential services operated on back-up power, a backlog is being experienced, as some services had to be facilitated manually," said spokesperson Unathi Batyashe-Fillis in a statement.
Travellers were asked to be patient, to cooperate with officials, and to call their airlines for flight information.
Eskom earlier announced power cuts were scheduled to last from 09:00 and 22:00 across the country due to seven days of heavy rain leaving coal stocks wet.
Consumers were urged to switch off all non-essential appliances.