Complex sentence: Improvements to future development aircraft, such as swept wings and more powerful Pegasus engines, led to the development of the Kestrel, which was evaluated by the Tri-partite Evaluation Squadron, made up of military pilots from Britain, the United States, and West Germany.
Split into simpler sentences: Improvements to future development aircraft, such as swept wings and more powerful Pegasus engines, led to the development of the Kestrel. The Kestrel which was evaluated by the Tri-partite Evaluation Squadron, made up of military pilots from Britain, the United States, and West Germany.