On 16 September 1975 the Spanish Ministerio del Aire signed a contract with CASA for the development of a new jet trainer capable of carrying a wide range of weapons. Design was assisted by Northrop (USA) and MBB (West Germany), but after the completion of the flight development programme, which began on 27 June 1977, the entire production was handled by CASA, except for items such as the US powerplant and Dowty Rotol nose landing gear.
Features include a low-powered turbofan of good fuel economy, tandem stepped seating with Martin-Beker zero/zero seats, manual controls apart from powered ailerons, and a large bay in the belly into which can be fitted a range of stores packages.
CASA initially delivered 60 C.101EB-01s for the Spanish air force, which gained the designation E.25 Mirlo. A second contract covered a further 28 aircraft and all surviving machines received a nav/attack system upgrade between 1990-1992.
Fitted with a 16.46-kN thrust TFE731-3 engine and provision for full armament, the C.101BB was the original export model. Chile became the first export customer; it received 14 C.101BB-02s, four Spanish-built and ten assembled by ENAER. Locally designated T-36 Halcon (hawk), these were intended for advanced training but were later modified with ranging radar to serve as A-36BB tactical weapons trainers.
First flown on 16 November 1983, the C.101CC dedicated attack variant introduced an uprated 20.91 kN thrust TFE731-5-1J engine. Exports have been made to Chile (23 C.101CC-02), Honduras (four C.101BB-03) and Jordan (16 C.101CC-04).
The C.101DD is the most advanced Aviojet variant. First flown on 25 May 1985, it has HOTAS controls, a HUD and compatibility with the AGM-65 Maverick ASM. Intended as an improved trainer with a secondary light attack capability, it has failed to gain orders.