Members of US Antarctic program arriving by C17 at a temporary sea ice airfield for the US base at McMurdo Station, Antarctica. This is the world's only seasonal sea ice airfield and is used early in the austral spring season when the ice is firm enough to support the weight of heavy-lift cargo aircraft. The ice flexes under the weight of these large aircraft and is closely monitored for safety. As the season progresses and sea ice starts to weaken, all the airfield equipment (radar dome, control tower, fuel tanks, etc.) which are mounted on sleds, are dragged by bulldozers to a more stable but distant location.