• They were accompanying a team who had just flown a four-seater Sling 4 plane from Cape Town to Cairo.
• They had been expected to land back in South Africa on Monday.
Two South African pilots behind a project that saw teenage students fly a homemade aircraft across Africa have been killed in a plane crash in western Tanzania.
Des Werner and Werner Froneman were in a support plane following the teenagers that went down in Tabora region.
They were accompanying a team who had just flown a four-seater Sling 4 plane from Cape Town to Cairo.
They had been expected to land back in South Africa on Monday.
Tanzania authorities said the plane went down on Saturday after take-off from Tabora airport.
The pilots sent a distress signal about engine failure before disappearing from radar, according to the Tanzania Civil Aviation Authority.
The plane was completely destroyed with only a few parts recovered, local authorities said.
It was owned by U Dream Global, an organisation founded by 17-year-old Megan Werner, Des Werner's daughter.
"Cape to Cairo Challenge is devastated to report that there has been an accident of the flight support aircraft and that the Project Directors, Des Werner and Werner Froneman, have lost their lives. No-one else was involved in the accident," U Dream Global said in a statement on Facebook.
The four-seater Sling 4 plane flown by the teenagers was assembled by a group of 20 students from vastly different backgrounds.
Miss Werner started the organisation to inspire young people.
For the inaugural Cape Town to Cairo flight in June, six teenagers - including Miss Werner - obtained pilots' licences and shared flying duties to cover the 12,000km (7,400 miles) to the Egyptian capital.
The young pilots' goal was to give motivational talks to other teenagers along the way.
They landed in Namibia, Malawi, Ethiopia, Zanzibar, Tanzania and Uganda during their three-week journey.
The teenagers built the aircraft in three weeks from a kit manufactured in South Africa by the Airplane Factory. Construction included assembling thousands of small parts.