"They're top guys. Something has gone tragically wrong. I won't speculate on the cause [because] everyone wants to speculate on plane crashes."
It's understood they were leading the safari - the third trip Mr Primrose had organised - when the tragedy occurred on Thursday.
The South African news website Beeld.com reported the aircraft might have been caught in a strong gust before it slammed into the mountains.
Witnesses reportedly saw one of the planes "struggling" and soon after heard a loud bang.
An air force helicopter found the wreckage on Thursday afternoon.
Crew on a medical helicopter that went to the crash scene found the plane had crashed in an area of thick clay and bush.
Mpumalanga police spokesman Colonel Leonard Hlathi said an investigation had started.
Mr Primrose was an experienced pilot but it was not known last night which of the men was at the controls.
Friend Phil Pacey said: "I've got nothing bad to say about Richard. I'm just so disappointed the whole thing has happened.
"He was very passionate about the trips in South Africa and wanted to share it - they were marvellous and, having done one, I can say it was incredible."
Mr Pacey travelled with Mr Primrose to South Africa two years ago.
"There were five couples in five Cessna 182s, and we flew through South Africa, Botswana, down the Zambesi River across Zimbabwe and back through South Africa again.
"You land at out-of-the way game reserves. It's amazing to see Victoria Falls from the air, it's absolutely something special ... And Richard was so keen on it and wanted to share it with everybody."
Despite the crash, Mr Pacey still believed flying was a far safer option than driving throughout Africa.
"It's arguably safer to fly around than drive around in New Zealand, and especially South Africa.
"If you were going to drive over that route you are more likely to die driving than you are in an aeroplane."
The plane went down near the town of Matibidi.
The Ministry of Foreign Affairs said it was providing consular assistance to the two men's families.
- additional reporting: Amelia Wade
