Vonlanthen started in Formula Vee, before progressing to Formula Three, where he won the Swiss Formula 3 Championship. He found things a little tougher in Formula Two, but managed to secure a seat with Frank Williams for the non-championship Swiss Grand Prix in 1975, where he finished 14th. He also made a World Championship start in the 1975 Austrian Grand Prix. Vonlanthen can be considered lucky to have started this race, as he was only allowed to start when Wilson Fittipaldi suffered an injury in practice which prevented him from taking his place on the grid.