Dr Bishop's friends and family gathered last night to pray for the three missing men.
Dr Bishop, 53, started climbing as a medical student some 30 years ago. On two previous trips to New Zealand, he'd had to turn back from Mt Cook after nearing the summit, Joshua Bishop said.
"Cook's something he's really wanted to do. On Christmas Day, he was like: This is it. We've got a good period of weather coming up and this will be the time to do it."
Missing climber Mike Bishop. His son said he was an experienced climber and would have gone out prepared. Photo / Supplied
Dr Bishop hadn't planned to climb with the Viellehners but after meeting them they had decided to summit together.
Joshua believed the three met at Plateau Hut.
Joshua was confident his dad was prepared but said an injury among any of the three could complicate efforts to find shelter.
"He's very safe ... He goes out there with the right gear. He doesn't go unprepared.
"One time he got caught in a big snowstorm and he had to make an igloo, or a snow cave, and he did it and survived and came back with all his limbs and fingers ... so he did the right job.
Joshua said it was good the three men were together, combining different kinds of expertise.
He believed Johann Viellehner, 58, had climbing experience in cold parts of Russia. Raphael Viellehner was 27, the same age as Joshua.
"I have complete confidence the three of them would have put their heads together and said: Let's find a cave, let's make something to stay warm."
Joshua said the efforts of authorities and volunteers in New Zealand were heartening.