North American Aviation Mustang Mk.I AG346 at Speke Aerodrome, November 1941 Published on October 25, 2012 in 26 October 1940Full resolution (577 × 434) ← Previous Next → The first production Mustang Mk.I, AG346, flew for the first time 10 April 1941, just xxx days after the first flight of the prototype, NA-73X. (Royal Air Force)