However, no orders were forthcoming from Germany as it had committed to buying American fighters (F4 Phantom and F-104 Starfighter) which included a deal for pilot training in the United States.

The Royal Thai Air Force operates the FT400 and FT600 versions, using it to train ab initio pilots who then went on to fly the Northrop F-5E fighter aircraft.

During 1970, the company announced that it had embarked upon a new project to develop a two-seat ducted-fan military trainer, intending to offer an aircraft that possessed jet-like handling at a low cost.

In March 1975, RFB received a contract from the German Defence Ministry to produce and fly a pair of prototype Fantrainers; these would be evaluated as replacements for Luftwaffe's existing fleet of Piaggio P.149 initial trainers.

[2] On 27 October 1977, the first prototype (registration D-EATJ), powered by a pair of EA871 110 kW (150 hp) NSU Wankel engines, made its maiden flight.

[5] During 1983, the prototype was refitted, its seven-bladed ducted fan being substituted for a five-bladed production standard counterpart, while the cockpit was also improved; the changes reportedly enabled a significant noise reduction and superior external visibility.

[8] During 2010, the company purchased all documentation related to the design, testing and type certification of the original aircraft, followed by the acquisition of associated tools, spare parts inventory, and the trademarks for Rhein-Flugzeugbau and Vereinigte Flugtechnische Werke.

FanJet Aviation believes that, following the adoption of a glass cockpit to modernise it, the aircraft remains both valid and cost-competitive for current-day pilot training purposes compared to contemporary jet-powered competitors.

Furthermore, RFB has claimed the type to be one-fifth as expensive to procure as the Cessna T-37 Tweet, a rival trainer, while delivering comparable performance (except for a slower top speed) at one-tenth of the fuel consumption.

[10] The use of a foam-plastic rubbing strip enables the fan to maintain the optimum blade-tip-to-shroud gap, said to be one-thousandth of the fan's diameter according to RFB; the ring slot ensures smooth air flow even at high power and low airspeed, and can also open asymmetrically to cope with offset inflow when the Fantrainer is flown at a relatively high angle of attack.

Typically, the cockpit is relatively spacious, providing room for a sizable instrumentation panel and ample side consoles, allowing the Fantrainer to be equipped akin to an air force's operational aircraft.