He won the FIS Ski Flying World Championships 1983 in Harrachov. Ostwald earned two medals in the team large hill at the FIS Nordic World Ski Championships with a silver in 1984 and a bronze in 1985. His best individual finish at the world championships was 4th in the individual large hill in 1982. His best finish at the Winter Olympics was 13th in the normal hill at Sarajevo in 1984. He also had World Cup wins.