the experimental aircraft association, headquartered in oshkosh, holds a yearly air show called "airventure oshkosh". it is mainly for experimental and recreational aircraft. the event has been held at oshkosh since 1970. the large number of planes coming and going during the fly-in week makes the wittman field air traffic control tower the busiest in the world. the event has become so popular that fans simply call it "oshkosh".