Complex sentence: This changed the aircraft's aerodynamic characteristics so that it became uncontrollable which in turn resulted in overstressing of the wings and tailplane leading to inflight structural failure, both wings and tailplane becoming detached from the fuselage.
Split into simpler sentences: This changed the aircraft's aerodynamic characteristics so that it became uncontrollable. This in turn resulted in overstressing of the wings and tailplane leading to inflight structural failure, with both wings and tailplane detaching from the fuselage.