The Dornier Do-28 Skyservant was developed into a number of progressively improved variants, from the original D, through the D1 and D2, to the 128-2, introduced in 1980. Each variant introduced a number of detail changes. Most Do-28 production was for military customers, notably Germany, although a small number were delivered to commercial operators.

The Dornier Do-28 was basically a two-engine version of the earlier Do-27 STOL aircraft series, which itself was based on the Do-25. The single Do-28 (or Do 28A) prototype was powered by two 132 kW/180 hp engines, and flew for the first time on April 29, 1959, still using a Do-27 wing.

The Do-28D was similar in layout to the Do-28A and Do-28B, but was considerably larger and heavier.

The main difference to the earlier Do-28D-1 was its higher gross weight, refined flaps, ailerons, stabilators and leading edge slats. Additionally, equipment that was previously only optional became standard on this model.

One Bundeswehr Do-28D-2 was modified with turboprops as Do-28D-2T, and flew for the first time in this configuration in March 1980, but no other Bundeswehr aircraft were re-engined. Two Marineflieger (Navy) Do-28D-2 were modified as Do-28D-2/OU (Oil Unit) for Oil Spill Search and Environmental Pollution Control. A Maritime Patrol version with a large radom under the nose/forward fuselage, was never sold and only a prototype was built.

Another Do-128-2 was used as testbed for the Dornier TNT (Tragfluegel Neuer Technologie = New Technology Wing) supercritical wing, and was equipped with two Garrett AiResearch TPE 331-5 turboprops (533 kW/with 715 shp). This layout was later also used on the Do-228, which was originally designated Do 28E-1 (15-seat Do 228-100) and Do 28E-2 (19-seat Do 228-200).

Air America

The main task of Air America’s Do-28s seems to have been communications flights and to transport small goods to outlaying villages in Laos. Often, the Dornier was called in to go into strips the Apache was originally intended to utilize, but could not. Later, those Do-28s which were based in South Vietnam and at Bangkok were used for similar types of missions. USAID was officially the main contractor to Air America in South Vietnam, all CIA missions in South Vietnam were flown as part of the USAID contracts, and within those contracts, all CIA requirements were handled with priority.