Within 21 months of the contract having been signed, the first prototype took flight on 16 August 1980, bearing the FAB serial 1300. The second prototype flew for the first time on 10 December 1980, implementing system accessibility enhancements to trim down maintenance overheads. Weapons captive flight trials resulted in the addition of a fin fillet to improve lateral stability. In August 1982, the second prototype was lost during clearance trials, in which full rudder was applied when the type exceeded the maximum designed diving speed (Vd) of by , causing the leading edge skin to tear apart, followed by a −30g dive, resulting in a complete disintegration of the airframe. Both the pilot and co-pilot were able to safely eject. The tailplane leading edge of the first prototype was modified, and requirements were cleared in 1983, after which it achieved a maximum diving speed of .