Transport minister Fikile Mbalula has ordered an independent inquiry following the release of a preliminary report on a fatal plane crash in January.

Three people - all pilots with the South African Civil Aviation Authority (SACAA) - were killed when a flight inspection aircraft crashed into a mountainside near George in the southern Cape on January 23.

The Accident and Incident Investigations Division (AIID) released the preliminary report on Monday.

"I welcome this report, published within the mandatory 30 days, and note that the investigation continues. It is imperative that we conclude the investigation as speedily as possible in order to give the families of the deceased closure," said Mbalula.

He said he had noted that the AIID, in conducting this investigation, had taken "reasonable" measures to ensure independence and objectivity.

This, he said, included the appointment of an independent expert, who is a former managing director of the US National Transportation Safety Board.

"I am equally mindful of the concerns raised by the families on the potential conflict of interest on the part of the South African Civil Aviation Authority, due to the fact that the aircraft in question belonged to SACAA and the personnel who manned the flight were SACAA employees," said Mbalula.

"Having considered the preliminary report, I have deemed it appropriate and directed that an independent inquiry be undertaken, considering that the aircraft belonged to SACAA and in order to be compliant with the legal principle of nemo iudex in re sua causa (no-one is judge in his own cause).

"In the coming weeks, arrangements to appoint an independent authority to take the investigation to its logical conclusion will be expedited in line with the ICAO [International Civil Aviation Organisation] prescripts, and details thereof will be made public.

"We are committed to ensuring that this investigation is finalised as quickly as possible."