The J75 was somewhat larger than the J57 in the F-102A, and had greater mass flow. This demanded changes to the inlets to allow more airflow, and this led to the further refinement of using a variable-geometry inlet duct to allow the intakes to be tuned to best performance across a wide range of supersonic speeds. This change also led to the ducts being somewhat shorter. The fuselage grew slightly longer, and was cleaned up and simplified in many ways. The wing was slightly enlarged in area, and a redesigned vertical tail surface was used. The engine's 2-position afterburner exhaust nozzle was also used for idle thrust control. The nozzle was held open reducing idle thrust by 40% giving slower taxiing and less brake wear.