20 Francs Transalpine flight

This issue commemorates the first transalpine airmail flight, completed by Oskar Bider on July 13, 1913, crossing the Alps from Bern to Milan in a Blériot XI monoplane. Bider completed the crossing in just over three hours despite significant turbulence and near-zero navigational aids — he used railway lines as ground references. The centenary made 2013 a natural occasion for Swiss authorities to recognize a flight that predated regular airmail service in Switzerland by nearly a decade.