A FlySafair flight had to circle Robben Island for almost two hours on Thursday to burn off fuel so it could land safely when a technical error was detected shortly after take-off, the company said.
In a statement released on its Twitter account, the low-cost airline said flight FA102 left Cape Town for Johannesburg at 17:32, but quickly realised that there may be a technical issue with an aircraft system.
As a precaution, the crew decided to return to Cape Town to investigate the issue.
"Unfortunately, the aircraft was in excess of the maximum landing weight permitted for a Boeing 737-400, so the crew were forced to maintain a holding pattern above Robben Island to burn off excess fuel so as to be light enough to land safely," the statement said.
"Boeing 737-400 aircraft cannot dump fuel."
Spokesperson Kirby Gordan told News24 that an aircraft can take off heavier than they can safely land. He said this particular one was full of fuel, which meant it was too heavy to land immediately.
'FlySafair nearly killed us'
He said the problem was a hydraulics system that has to do with fine control on one of the wing flaps and was "nothing as drastic as landing gear".
Cape Town International Airport air traffic control was alerted, and after just under two hours, the passengers and crew landed safely again.
Gordan said it was a normal landing, not an emergency landing, but "assistance" vehicles were on hand, in line with standard procedure.
The aircraft was taken to a bay where passengers had to disembark. They were then taken to another aircraft to start the trip to Johannesburg again.
This means passengers waiting for flight FA103 from Johannesburg back to Cape Town will now depart at 23:50 and land at 02:05. The flight was scheduled to depart at 20:15 and land at 22:30.
Passengers on this flight were invited to report to the ticket sales desk for a meal voucher for something to eat while they wait. FlySafair apologised for the incident and thanked passengers for their patience.