Kenya specialist, African Safari Club, is withdrawing its in-house airline African Safari Airways from Gatwick from November.
Instead, it will use a once weekly service with Monarch Airlines for its UK to Mombasa flights.
It says the move will allow African Safari Airways to "better serve its European gateways".
Daniel Sykes, director of sales, marketing and business development at African Safari Club, said: "The decision to move our UK - Mombasa flying to Monarch has been a simple one.
"We have already established an excellent relationship with the airline via our Nile River Cruise programme, which is also set for expansion in November to include operations from both Manchester and Gatwick."
African Safari Club will use additional seats from First Choice, TUI and Kenya Airways on selected dates to meet the demands of their Indian Ocean Cruise programme aboard the MS Royal Star.
Customers affected will be offered the alternative flight, the opportunity to change their holiday dates or a full refund of all monies paid.