There were major delays affecting departures and arrivals at the OR Tambo International Airport and the rest of the network at South African airports.
The news came as travellers anticipated some relief following the end of the pilots strike at domestic airline FlySafair.
Flights resumed yesterday in full force following the nearly two-week long strike by pilots for better wages and work-life balance rosters.
On Friday evening, ATNS released a statement assuring passengers that it was working to actively addressing the backlog of delayed departures and arrivals.
Passengers are advised to continue to check with airlines for updated flight information, use the ACSA Airports Company South Africa Mobile App for real-time notifications and arrive early for flight departures, read the statement.