Prince Carl Gustaf was also given the title of the Duke of Jämtland . His father , Prince Gustaf Adolf , Duke of Västerbotten was killed in an airplane crash on 26 January 1947 , at Copenhagen Airport . His father 's death had left the nine-month-old prince second in line for the throne , behind his grandfather , then Crown Prince Gustaf Adolf . When his paternal great-grandfather Gustaf V died in 1950 , the four-year-old prince became the heir apparent of Sweden
airplane crash
1947 KLM Douglas DC-3 Copenhagen accident
Carl XVI Gustaf of Sweden