The flight path of the Hercules passed over the iceberg-littered Ross Sea, then the Japanese and Korean Antarctic bases, and the site for a new Chinese base on the ice.
When the aircraft dropped below the clouds, Mt Erebus - where 257 people on an Air NZ jet were killed in a crash in 1979 - was visible.
Mr Key said: "I think Erebus will always have a special place in their hearts. Most people can remember the first time they learnt about the loss of our aircraft down here.
"I know I was starting School C at around that time - it's a memory that's lasted with me till now."
Mr Key also explained his collapse at the Tutto Bene pizzeria in Christchurch on Thursday, which resulted in a trip to Christchurch Hospital.
"It was a very normal meal and normal evening. About 15 minutes before we were due to go, for reasons I can't explain, I broke into this heavy sweat.
"I got up to go when we were leaving the restaurant and [wife] Bronagh came up to me and say, 'Are you OK?' Apparently I didn't answer and just collapsed," the PM said.
Specialists at the hospital told him the incident was a "one-off".
Mr Key said the Government was still considering whether to increase its $26 million funding for Antarctic activities, but he was keen on support from the private sector.
He also spoke of the importance of United States-NZ collaborations, in particular the Andrill project, which involves drilling into the ice core to build up a record of the climate over millions of years.
NZ is keen to support a second phase of the project, and has offered to fund 12.5 per cent of it.
