The Dornier Merkur Switzerland at the old Aswan dam, probably late in December 1926. Flight to the Cape with Walter Mittelholzer, Hans Hartmann, René Gouzy and Arnold Heim. Photo by: Arnold Heim / ETH-Bibliothek Zürich

Pioneering Swiss company Ad Astra Aero operated a seaplane station on Zürichhorn, near the Tiefenbrunnen public bath. Departing on 7 December 1926, pilot and photographer Walter Mittelholzer flew CH-171 Switzerland from Zürich to Cape Town via the Nile with his co-pilot and mechanic Hans Hartmann, René Gouzy and geologist Arnold Heim. Photo from: ETH-Bibliothek Zürich

Lufthansa had 30 Merkurs at some point.

Carrying mail and one passenger from Hamburg on 14 March 1929, the crew could not find Cologne in fog and came down in a muddy field across the Dutch border, near Schaesberg, now part of Landgraaf. The worst damage was a broken propeller and the aircraft could be flown out two days later from a straw-covered strip. Photo from: Nationaal Archief (Netherlands)

The Do B Merkur was a development of the Do C Komet. It could carry six to eight passengers. Ad Astra merged with Balair to form Swissair in March 1931, by which time its two Merkurs were no longer in revenue service. Photo from: ETH-Bibliothek Zürich