B-25 Mitchell “Killer Bee”

The North American B-25 Mitchell is a medium bomber that was introduced in 1941 and named in honor of Major General William “Billy” Mitchell, a pioneer of U.S. military aviation. Used by many Allied air forces, the B-25 served in every theater of World War II, and after the war ended, many remained in service, operating across four decades. Produced in numerous variants, nearly 10,000 B-25s were built. These included a few limited models such as the F-10 reconnaissance aircraft, the AT-24 crew trainers, and the United States Marine Corps’ PBJ-1 patrol bomber.

The Air Corps issued a specification for a medium bomber in March 1939 that was capable of carrying a payload of 2,400 lb (1,100 kg) over 1,200 mi (1,900 km) at 300 mph (480 km/h) North American Aviation used its NA-40B design to develop the NA-62, which competed for the medium bomber contract. No YB-25 was available for prototype service tests. In September 1939, the Air Corps ordered the NA-62 into production as the B-25, along with the other new Air Corps medium bomber, the Martin B-26 Marauder “off the drawing board”. Early into B-25 production, NAA incorporated a significant redesign to the wing dihedral. The first nine aircraft had a constant dihedral, meaning the wing had a consistent, upward angle from the fuselage to the wingtip. This design caused stability problems. “Flattening” the outer wing panels by giving them a slight anhedral angle just outboard of the engine nacelles nullified the problem and gave the B-25 its gull-wing configuration. Less noticeable changes during this period included an increase in the size of the tail fins and a decrease in their inward tilt at their tops.