He made the first North-South flight across Africa. It took him 77 days. Mittelholzer started in Zürich on December 7, 1926, flying via Alexandria and landing in Cape Town on February 21, 1927. Earlier, he had been the first to do serious aerial reconnaissance of Spitsbergen, in a Junkers monoplane, in 1923. On December 15, 1929 he became the first person to fly over Mount Kilimanjaro, and planned to fly over Mount Everest in 1930. In 1931, Mittelholzer was appointed technical director of the new airline called Swissair, formed from the merger of Ad Astra Aero and Balair. Throughout his life he published many books of aerial photographs and marketed his expeditions through films and the media as well. He died in 1937 in a climbing accident on an expedition in the Hochschwab massif in southwest face of Stangenwand in Styria, Austria.