[2] According to the aviation historian Jörg Armin Kranzhoff, the company had become confident enough of an order for new twin-seat trainer aircraft from the German government that, by 1930, it had directed the production of multiple project designs to fulfil this anticipated demand.

[2] Despite this confidence, the Deutsche Verkehrsfliegerschule, a German covert military-training organization, lacked financial resources and thus did not act quickly to issue any such contract.

[2] Licenses to produce the Ar 66 were issued to multiple German aircraft manufacturers, including MIAG, 90 for Bayerische Flugzeugwerke AG[3] and Gothaer Waggonfabrik.

The aircraft was typically operated by crew of two: instructor pilot and trainee, which were seated in open tandem cockpits; both positions were equipped with dual flight controls.

[1] It was powered by a single Argus As 10C air-cooled inverted V8 engine, which produced roughly 179 kW (240 hp) and drove a 2.5 m (8.2 ft) two-blade propeller.

Construction consisted of a double pine wing spar structure, with lime tree ribs, and fabric covering.

[2] According to Kranzhoff, the most unique feature of Ar 66 was the unusually high horizontal stabilizers, which was also mounted on the upper surface of the fuselage at an atypically forward position.

[1] An improved undercarriage arrangement was adopted for production aircraft; this included low-pressure tyres, wheel brakes, and oil-cushioned spring struts.

[6] Arado decided to capitalise on the positive reputation of the Ar 66; for the first time, it published a wide range of advertisements across multiple languages centred on the aircraft.

[1][4][3] Data from Aircraft of the Third Reich[1] At the end of World War 2, several Arado 66C belonging to 3./ Nachtschlactgruppe 8 were abandoned at Bardufoss, in Norway.

Eventually the remains of several aircraft were collected by the Forsvarsmuseet (National Defence Museum) of Norway and transported to Gardermoen outside Oslo.