The Prime Minister hopes to step in Captain Robert Falcon Scott's historic footprints when he visits the South Pole for the first time on Saturday.
He and wife Bronagh, accompanied by Antarctica New Zealand chairman Rob Fenwick and diplomatic protection officers, will visit the United States' Amundsen-Scott South Pole Base to learn about its scientific projects.
It is 101 years and two days since Scott's five-man team reached the South Pole, only to discover Norwegian explorer Roald Amundsen had claimed the world's first 34 days earlier.
However, Key's six-hour return flight on Saturday in a United States Hercules plane is a world away from Scott's gruelling 78-day mission to reach the pole.
He said on Friday his South Pole visit would be the trip's highlight and he hoped he would get the chance to venture where Scott trod more than a century earlier.
"It would be pretty amazing.''
In contrast, Scott wrote that day in 1913 on arrival to the South Pole:
"Great God this is an awful place and terrible enough for us to have laboured to it without the reward of priority."
The men died on their return journey of exhaustion, cold and starvation.
Key's planned four-day trip was thrown into disarray after fog on the frozen continent delayed his original departure on Thursday evening but then he later collapsed at a Christchurch restaurant.
He was taken to Christchurch Hospital's emergency department but doctors decided that night he had only fainted and cleared him for his Antarctica travels.
After his South Pole visit, Key will host a dinner for US guests at New Zealand's Scott Base tonight as part of his promotion of the strong bond between New Zealand and the US in Antarctica.
It is a bond that has been tested in recent months after the two nations disagreed over toothfishing in the Southern Oceans.
Key's itinerary has been shortened to only three days but he will still venture to the Dry Valleys on Sunday to promote scientific research into climate change by the newly-created public-private partnership New Zealand Antarctic Research Institute, which he launched last August.
- Fairfax Media