 Complete the following phrase:  The most prestigious event in ski flying is the World Championships, which was first held in Planica in 1972 and has been staged biennially since 1988, in a rotating schedule at all hills except Ironwood. The World Championships replaced various incarnations of International Ski Flying Week, which ran from 1953 to 1989. Gold, silver and bronze medals are awarded after two competitions, with the total points winner receiving the title of Ski Flying World Champion. A team competition was introduced in 