Ms Sacco is the director of corporate communications at IAC, a company which owns a number of popular websites including OKCupid, The Daily Beast, Vimeo and Tinder.
The Twitter account has since been deleted after having no activity for a number of hours, supposedly while she was on the flight.
In response to the furour, IAC has removed Ms Sacco’s details from its corporate website, but not commented on her employment status. Many Twitter users have called on the company to fire Ms Sacco following the comments.
“This is an outrageous, offensive comment that does not reflect the views and values of IAC,” the firm said in a statement on Friday.
“Unfortunately, the employee in question is unreachable on an international flight, but this is a very serious matter and we are taking appropriate action.”
By Friday evening the Twitter hashtag #HasJustineLandedYet was trending on the social media site, with many speculating what would happen when she realised the backlash she had received.
Many Twitter uses also pointed to the ironic fact that Ms Sacco works in public relations for an Internet company.
David Cohn wrote: “Is that tweet real? You work in PR. You shld know better RT @JustineSacco “Going to Africa. Hope I don't get AIDS. Just kidding. I'm white!””
While another commented: “@JustineSacco Let me know how fast it takes your white ass to get fired.”
The tweet isn’t the latest in a string controversial comments Ms Sacco has made on the site.
Hours before, she had called London the home of “cucumber sandwiches” and “bad teeth,” while she has previously tweeted “I like animals, but when it’s this cold out I’ll skin one myself for the fur” - at the animal rights group PETA.
In January Ms Sacco tweeted: “I can’t be fired for things I say while intoxicated right?”