COPPER MOUNTAIN — Big air soared into the big time Sunday, with the first-ever snowboarding contest in U.S. Grand Prix history, a high-flying world cup competition that also served as the first step in Olympic qualifying for snowboarders seeking to compete in the sport’s debut in the PyeongChang Winter Games. Three American slopestyle snowboarders took a step toward South Korea: Connecticut’s Julia Marino, Silverthorne’s Chris Corning and California’s Chandler Hunt.