A woman was reportedly removed from a Kulula flight on Friday evening, after another passenger heard her call the pilot the K-word.
Nadine Watkins, who was on the fight, tweeted that the plane had turned back to O.R Tambo, after an "unsavoury passenger called the captain the K-word."
"Our flight might be 10 minutes late, but as South Africans we can't allow this type of behaviour to continue," she tweeted.
Elaborating on the incident in a follow up tweet, Watkins said the woman had apparently been on her phone with her boyfriend, and the passenger sitting next to her had overheard her calling the pilot the K-word.
"He alerted the flight attended (sic) before lift off and they got security to remove her," she said.
Kulula spokesperson, William Smook confirmed an incident had taken place.
"We can confirm that there was an incident involving a passenger aboard one of our flights. We're investigating it. We don't tolerate discrimination in any form."
"Our crew are entitled to do their jobs without verbal abuse," he said.