Heli-skiing is off-trail, downhill skiing or snowboarding that is accessed by a helicopter, as opposed to a ski lift. As early as the late 1950s helicopters were used in Alaska and Europe to access remote terrain, but the birth of heli-skiing as a commercial sport is attributed to Hans Gmoser in 1965. Skiers board the helicopter and are carried to a landing zone on the mountain. Skis, snowboards and poles are generally carried in an exterior basket loaded and unloaded by a guide. Snow conditions on the mountains vary considerably over the course of the winter as the snow is subjected to sun, wind, temperature variation, and new snowfalls. Snow conditions change almost every day.