Complex sentence: In March 1913 he retourned to Switzerland, welcomed at the boundary in Basel as a much-admired'aviation hero', doing on March 9 the first airmail flight in Switzerland from Basel to Liestal.
Split into simpler sentences: In March 1913 he returned to Switzerland, welcomed at the boundary in Basel as a much-admired'aviation hero'. On March 9 he flew the first airmail flight in Switzerland from Basel to Liestal.