It looks like the furthest point from any airport is (not surprisingly) about the same place as Point Nemo (https://en.wikipedia.org/wiki/Pole_of_inaccessibilit

It looks like the furthest point from any airport is (not surprisingly) about the same place as Point Nemo (https://en.wikipedia.org/wiki/Pole_of_inaccessibility#Oceanic_pole_of_inaccessibility https://en.wikipedia.org/wiki/Pole_of_inaccessibility#Oceani...), the furthest point from land.