The French Armée de l'Air (AdA) ordered a two-seat Mirage IIIB operational trainer, which first flew in October 1959. The fuselage was stretched about a meter (3 ft 3.5 in) and both cannons were removed to accommodate the second seat. The IIIB had no radar, and provision for the SEPR rocket was deleted, although it could carry external stores. The AdA ordered 63 Mirage IIIBs (including the prototype), including five Mirage IIIB-1 trials aircraft, ten Mirage IIIB-2(RV) inflight refueling trainers with dummy nose probes, used for training Mirage IVA bomber pilots, and 20 Mirage IIIBEs, with the engine and some other features of the multi-role Mirage IIIE. One Mirage IIIB was fitted with a fly-by-wire flight control system in the mid-1970s and redesignated Mirage IIIB-SV (Stabilité Variable); this aircraft was used as a testbed for the system in the later Mirage 2000.