The first Komets (Do C III Komet I) utilised the same rectangular plan, 17 m (55 ft 9 in) span wing, tail, and even upper fuselage, as well as the 138 kW (185 hp) BMW IIIa engine of the Delphin I, but replaced the lower fuselage and sponsons with a simple sheet-metal bottom that incorporated fixed tailskid undercarriage.

[1][2] An improved version, the Do Komet II, was first flown on 9 October 1922 and was widely exported to countries including Colombia, Spain, Switzerland, and the Soviet Union.

The cabin was expanded to seat another two passengers and the larger wing, with a span of 19.6 m (64 ft 4 in), was raised above the fuselage on short struts.

The type was widely used by Deutsche Luft Hansa, which had some 30 Merkurs operating at one time, and was also exported to Brazil, China, Colombia, Japan, and Switzerland.

The Do C and Do D were follow-on military designs, the former was a trainer exported to Chile and Colombia while the latter was a floatplane torpedo bomber built for the Yugoslav Royal Navy.

[5] The arcraft was promoted for its ability to be used as an airliner, utility transport, air ambulance, aerial surveyor, in either a landplane or floatplane configuration.

Parts were joined together using riveting in a manner that permitted repairs and even total replacement to be readily performed by non-specialist workers.

[8] These struts enabled the wings to have a constant chord along with an invariable section of moderate thickness to suit the most favourable aerodynamic characteristics.

A pair of spars (composed of steel sections) and relatively sturdy box ribs, the latter eliminating the need for bracing of the former, absorbed the various forces exerted upon the wings.

Aft of the engine bay was the cockpit, which seated a pair of pilots provisioned with dual flight controls and comprehensive instrumentation for the era.