In his 9th World Cup race, Heinzer came 8th in the Hahnenkamm Downhill on January 17, 1981 for the first time in the World Cup, his first podium followed on March 6, 1981 in the downhill in Aspen . During his active time in the Ski World Cup between 1981 and 1994, he was able to celebrate numerous successes, especially in the downhill discipline . He won at least one race on the most important downhill courses ( Val-d'Isère , Wengen , Kitzbühel , Gröden , Garmisch-Partenkirchen , Aspen , Lake Louise ) and was on the podium a total of 17 times. Between 1991 and 1993 he won the Downhill World Cup three times in a row, and in 1991 the Super G World Cup.
His greatest success was winning the downhill world champion title in Saalbach-Hinterglemm in 1991 . Prior to that, Franz Heinzer had finished fourth at world championships at the World Cup downhill runs in Schladming (1982), Bormio (1985) and Crans-Montana (1987). In 1989 he failed in the team's internal qualification in Vail. At the 1994 Winter Olympics in Lillehammer , he only got a few meters because the ski binding broke right after the start. A few weeks later, Heinzer ended his career.
Since then he has headed a sporting goods market - currently in Altdorf - and has been looking after the Swiss downhill team as an assistant trainer since winter 2004.