Complex sentence: There are ways to improve this through better flap design, modern airliners use complex multi-part flaps for instance, but they tend to add considerable complexity and take up room on the outside of the wing, making them too difficult to use on a fighter.
Split into simpler sentences: There are ways to improve this, through better flap design: modern airliners use complex multi-part flaps for instance. However, large flaps tend to add considerable complexity, and take up room on the outside of the wing, which makes them unsutible for use on a fighter.