The B-25 Mitchell was perhaps the most successful medium bomber of WW II. Over 10,000 aircraft were produced and it was flown by most allied nations and in every theater of war. The Mitchell first entered USAAF service in the spring of 1939 and flew until 1960. The aircraft was used for another two decades by other air forces. Of course, it was the star of the 1942 Doolittle raid.