Complex sentence: On 21 March 1991, the prototype performed its maiden flight, after which it continued test flights for some time, demonstrating both the maturity of the concept and of the new IAI-integrated systems.
Split into simpler sentences: On 21 March 1991, the prototype performed its maiden flight. Following on from its first flight, it continued to be used for test flights for some time, demonstrating both the maturity of the concept and of the new IAI-integrated systems.