Jeff Hills and his son Matthew were found dead in the wreckage of their four-seater plane which crashed in steep terrain in Dorrigo National Park, near Coffs Harbour, on Saturday.

"They were incredibly generous of their time and their finances to support those in serious need within the Gold Coast community, interstate and overseas," Jeff's nephew Craig Cameron told reporters on Sunday.

"With Jeff's three sons Matt, Jamie and Josh by his side, the Hills boys together embraced life to the fullest.

"Yes, Jeff and Matt will be deeply missed, but we are comforted that they are living in eternity with Christ their saviour."

Jeff, in his 50s, and Matthew, in his 20s, set off from Murwillumbah in northern NSW at 6.30am on Friday and were scheduled to arrive in Taree at 8am.

Their associates, concerned the plane dropped off the radar and had not reached its destination, reached out on Friday morning to the Australian Maritime Safety Authority, which deployed its Melbourne-based search and rescue jet.

Poor weather and difficult conditions prevented search teams from locating and accessing the aircraft sooner.

The crash will be investigated by the Australian Transport Safety Bureau, which asked any witnesses to come forward.

"Should a critical safety issue be identified during the course of the investigation, the ATSB will immediately notify relevant stakeholders so appropriate and timely safety action can be taken," a spokesman said.

It's the second fatal plane crash in NSW in two weeks and the fifth nationwide in four months, according to ATSB data.

Australian Associated Press