The families of three Australians, including two Qantas pilots, injured in a fatal plane crash in South Africa, have arrived in their country to be by their bedside.

A vintage Convair-340 plane came down and crashed into a dairy farm during a flight in Pretoria on Tuesday, killing a South African crewman and injuring Qantas pilots Ross Kelly and Douglas Haywood, as well at 18 others.

A factory worker was seriously injured in the crash and later died.

Mr Kelly's brother is among family who have tonight arrived at the hospital, and told 9NEWS, the 64-year-old is in a critical condition, but has been deemed stable.

Ian Kelly, Ross's brother says the family is "very optimistic" as they await news on their conditions. Picture:9NEWS (9news)

The family of one of the Qantas pilots and his wife injured in a plane crash in South Africa, arrive at hospital. Picture:9NEWS (9NEWS)

"Doctors have told us to take it a day at a time," Ian Kelly said.

"We're very optimistic and hoping for the best".

Mr Kelly's wife Lyndal was also on board, and is in stable condition. She is still in an induced coma, but Ian said doctors are confident she'll make a full recovery.

The pairs' two children are also among the family who have arrived tonight in South Africa.

Ross Kelly, who recently retired, and his wife Lyndal, have been injured in the crash. Picture: Facebook (Facebook)

Pilot Douglas Haywood has also been injured. Picture: Facebook (Facebook)

"I'd like to pay tribute to all the airlines for getting us here; Virgin Australia, SAA, Qantas, they've all been absolutely marvellous in making this so much easier for us", Mr Kelly told 9NEWS.

Ross Kelly was making the short flight from Wonderboom Airport to Pilanesberg after it had been restored, before it was due to be flown to its new home - an aerospace musuem in the Netherlands.

The ABC reports that the flight was on a joyride , as a thank you to the team who had done the work.

A statement has been released by Qantas this morning.

"We were deeply upset to learn that two Qantas pilots, one current and one retired, were on board the vintage aircraft involved in an accident in South Africa on Tuesday," the statement read.

The short flight from Wonderboom Airport to Pilanesberg is believed to have been a weight test for the aircraft before it flew to its new home. Picture: Supplied (Supplied)

The plane crashed into a dairy farm. Picture: AAP (Supplied)

"This news has shocked the Qantas pilot community and everyone’s thoughts are with the families.

"We’ve reached out and are providing whatever support we can."

Both men have flown for Qantas for more than 30 years, including as A380 captains, with a combined 37,000 hours of flying experience.

A friend of Mr Kelly, who had recently retired, told 9NEWS he had been working on the project to rebuild the vintage aircraft for months.

(9news)

People rushing to the aid of those on board. Picture: Supplied (Supplied)

“Ross is among the most experienced pilots and was well versed in this sort of aircraft operations,” Andy Hardy said.

“He has ferried vintage aircraft from the US and Europe back to Australia several times.

Two people died and 20 others were injured. Picture: AP (AAP)