For the big McMurdo US base they have flown in a few times in the winter for extremely important life or death medical reasons (last year: Aug 25 [1]) For the smaller other country bases it tends to be too dangerous and impossible. They are not able to use mcmurdo and the americans cant help either.

The general rule is that the Americans don't fly during the winter but they do tend to downplay and not publicize the times when they do fly.

[1] https://www.theguardian.com/world/2025/aug/06/mcmurdo-statio...