It's very difficult terrain. It's thick jungle, low clouds,' he said.
The Australians aboard the Airlines PNG scheduled flight were tourists intending to walk the Kokoda Track, where Australian soldiers held back the Japanese advance in World War II.
Liz Holliday, whose son is among the missing, told ABC Radio that Peter Holliday intended to walk the Kokoda Track in the footsteps of his grandfather, who served there with the Australian forces.
'I guess it's the same for everyone, everyone who's got anyone missing, it's just totally devastating,' she said. 'So our heart goes out to everyone, all the families of everyone who's got someone missing.'