The company said this morning Aldrin was responding well to treatment and was in good spirits.
"He currently has fluid in his lungs but is responding well to antibiotics and being kept overnight for observation. His condition is stable and his manager, who is currently with him, described him being in good spirits."
The 86-year-old tourist arrived in Christchurch overnight after his health suddenly deteriorated, said the spokesman for the American polar programme.
NSF spokesman Peter West said a Safair cargo plane making the mercy dash to New Zealand touched down at Christchurch International Airport about 4:25am and he was transferred to Christchurch Hospital.
Aldrin was at the Amundsen-Scott Station at the South Pole when he fell ill.
Two doctors, one from the US Antarctic Programme, decided it was best to evacuate him off the ice.
He was first flown to McMurdo Station and then scheduled on the first available flight for Christchurch.
Before leaving for Antartica Aldrin posted pictures of himself and tour companions from a South African airport excited about the coming journey to the end of the earth.