North American’s first bomber design (indeed, it’s first multi-engine aircraft) was the NA-21, built as the XB-21 to compete against the improved B-18A Bolo. First flown in December 1936, the XB-21, with its two Twin Wasp engines, was an advanced design with powered nose and tail turrets. These proved troublesome and were removed, but once reengined with R-2180 Twin Hornets, the XB-21 showed good performance, with a top speed of 220 mph, a range of just under 2,000 miles, and a 10,000lb warload. However, the North American design was almost twice as expensive as the Bolo, and plans for the purchase of a handful of YB-21 service test aircraft were cancelled.

The company’s next try at a bomber design, the NA-40, had the same basic Twin Wasps as the original NA-21, but was otherwise quite different, with a high-mounted wing, slender fuselage with tandem seating, tricycle gear, and twin vertical tails. The NA-40 first flew in January 1939, but performance with the Twin Wasps was disappointing, and the prototype was quickly rebuilt as the NA-40B with R-2600 Twin Cyclones, flying with the new powerplants on 1 March 1939. Performance was improved, but there was little chance to show off the NA-40B before it was lost in an April 1940 crash.

North American was, on the surface, having little success with bombers, but the XB-21 and NA-40 experiences were to prove valuable, as the USAAC had issued a requirement for a new medium bomber even before the NA-40B’s loss. This called for an aircraft that could reach 300 mph, carry a ton and a half of bombs, and had a range of 2,000 miles. North American’s NA-62 contender for this requirement was clearly an NA-40B outgrowth, with a widened fuselage and lowered wing. This won a contract in September 1939 for 184 aircraft, and in September of the following year the prototype B-25 flew.

Variants

B-25B: Manned dorsal turret in place of the tail “stinger”, initially a remotely operated ventral turret.

B-25C: First Mitchell to be built in large numbers; R-2600-9 engines, 2x .50-cal in nose.

F-10: 45 B-25Ds with three K17 cameras in the nose; armament deleted. Four aircraft known to have been transferred to Canada.

XB-25E: B-25C deicing testbed, using hot air circulated from the engine exhausts.

XB-25F: B-25C testbed for electrical deicing

B-25G: Production gunship, with an M4 75mm field gun fitted in the solid nose for use in the anti-ship role

B-25H: Upgunned variant, with a quartet of .50-cals in added blister packs on the sides of the nose, and four more in the nose itself in addition to those carried in the waist positions and the turrets. The M4 was replaced by the T13E1 cannon, and the dorsal turret was also moved forward.

B-25J/Mitchell Mk. III: Ultimate new-build Mitchell, initially switching to the glass nose, with the dorsal turret relocated and the blister guns retained. Later aircraft had the bombardier’s position removed and a solid nose with eight guns fitted.

B-25 Bibliography
Photo: B-25s lined up at Inglewood Flight May 14, 1942 p.474
Rohm & Haas Company ad, with a photo of a glass-nose Mitchell Aviation July 1942 p.15
B.F. Goodrich ad, with color artwork depicting a group of B-25s striking a target Aviation November 1942 p.139
“Exploring the Aerial Arctic” Ad for Curtiss Electric Propellers, with color artwork depicting a B-25 with an icing test rig Aviation November 1943 p.155
Photo: close-up of a B-25 dorsal turret Aviation December 1943 p.431
Curtis Fuller “Three-Eyed Mapping” includes a closeup of a recon B-25’s nose, and a shot of the internal tri-metrogon camera equipment Flying January 1944 p.63
Alfred Friendly “Plane Cannibals” refit of a severely damaged B-25 Flying May 1944
Photo (small): B-25J 430646 with radar pod under nose and antennas beneath waist positions Aviation News July 22, 1946 p.7
“B-25 Tip Tanks Give Double Value” Aviation Week July 27, 1953 p.60
“The Catch-22 Air Force” Extensive photo coverage of the Mitchells used in the filming of Catch-22. Air Classics December 1972. Includes color photos of “Berlin Express”, “Laden Maiden”, “Dumbo” and “Free Fast Ready” nose art.
Photo: Lineup of RAF Mitchells, one having invasion stripes. RAF Yearbook 1984 p.58-59
Photo: Tallmantz N1042B with camera extended from bomb bay Aeroplane Monthly March 1987 p.127
Photo: B-25J in a dismantled state. Warbird International January/February 1989 p.40
d’Anis Elbied “B-25J Mitchell” Replic March 1994 Finishing the Italeri 1/72 Mitchell as a French aircraft. Includes cockpit photos and diagrams.
Photo: “Mitchell Rebuild” FlyPast March 1998 p.15 B-25J 43-35972
“B-25 emerges from the Undergrowth” Aeroplane September 2006 p.6 VB-25N N9089Z
Preview of the B-25B cockpit detail set for the 1/48 Italeri/Accurate Miniatures Mitchell kit. Skymodel 14/07 p.27
Photo: large color side view of B-25J 45-8882/N32T in red/black scheme Warbirds International Jan/Feb 2009 p.62-63
John Fox “B-25” AIR Modeller 33 building the 1/48 Italeri Mitchell
Preview: B-25J “Glass Nose” in 1/32 from HK Models Model Airplane International July 2012
Photo: color side-view of B-25 N9117Z in fire tanker markings Warbirds International April/May 2013 p.65
Rick Turner “Globetrotting with Eight-Seven Zulu” Warbirds International December 2013 numerous photos showing the post-military career of TB-25K 44-86873
John Lumley “Daisey Mae Mitchell Mk. 2” Model Aircraft April 2016 Kitbashing the Accurate Miniatures B-25C/D as a high-visibility postwar Canadian Mitchell.

Bill Gunston Encyclopedia of World Airpower Aerospace Publishing, 1980 p.283: color profile of a Uruguayan B-25J

Bill Gunston Aircraft of World War II Includes a scale 5-view illustration of a B-25J-1, and color profiles of the NA-40, a B-25 of the 17th BG, a Doolittle Raider B-25B, a PBJ-1D, an RAF Mitchell II, F-10 reconnaissance model, a Chinese B-25H, and a Soviet B-25J.

Bill Gunston Illustrated Encyclopedia of Combat Aircraft of World War II p.247 color in-flight photo of camouflaged B-25J 431162 in Soviet markings

David Mondey The Hamlyn Concise Guide to American Aircraft of World War II p.191-195: Color profiles of a B-25A of the 34th BS, B-25Cs from the 81st, 487th, and 488th Bomb Squadrons, Mitchell Mk. IIs of No 226 and 320 Squadrons, B-25Js of the 498th and 499th Bomb Squadrons, Netherlands, and the RAAF.

Dana Bell Air Force Colors Vol.1 1926-1942 p.77: color profile of a 17th BG B-25B

David Gero Military Aviation Disasters – Significant Losses Since 1908 Haynes Publishing p.34-35: An account of the 1945 crash of a B-25 into the Empire State Building, and a photo of the aftermath.

Yefim Gordon, Sergey Komissarov, Dmitry Komissarov German Aircraft in the Soviet Union and Russia p.282: Photo of a Soviet Lend-Lease B-25J used during the DFS 346 program

Jerry Scutts PBJ Mitchell Units of the Pacific War Includes PBJ-1J and -1H 1/72 scale side view drawings

Steve Pace B-25 Mitchell Units of the MTO includes 1/72 scale side view drawings of the B-25C, B-25D, B-25G, B-25H, and B-25J

Chris Bishop The Encyclopedia of 20th Century Air Warfare p.233: color 3-view of B-25J Betty’s Dream

Aircraft Anatomy of World War II: Technical Drawings of Key Aircraft 1939-1945 Paul Eden, Soph Moeing, editors p.82-85: B-25H cutaway, artwork showing B-25D Dirty Gertie from Bizerte