 Other improvements were made in parallel with the A-36, including an improved, fixed air duct inlet replacing the movable fitting of previous Mustang models and the fitting of wing racks able to carry either drop tanks, increasing the maximum ferry range to with the tanks.The top speed was raised to at .The USAAF received 310 and the RAF 50 (as the Mustang II) before production converted to producing the Merlin-powered P-51B.