update (05 Feb 2013): AfricaStay has teamed up with South African low-cost carrier Mango to operate charter flights to Zanzibar. From 12 March 2013 AfricaStay will offer charter flights on every Tuesday between South Africa (Johannesburg?) and Zanzibar (same-day return). A Saturday-operated flight is also planned over December. According to Tourism Update, the flights will be well priced and it will be possible to book flights only.
According to ch-aviation.ch, South African budget airline Mango is planning to launch a weekly serice between Johannesburg and Zanzibar from 26 February 2013. The airline has already published schedules for flights to its first international destination, but has not yet started taking reservations.
Mango, a state-owned subsidiary of South African Airways, is currently South Africa's most punctual domestic airline and the only airline in Africa offering on-board Wi-Fi. The carrier is operating scheduled budget services to and from OR Tambo International Airport and Lanseria International Aiport in Johannesburg, as well as to and from Bloemfontein, Cape Town, Durban and Port Elizabeth.