;Boston I & II: The
Royal Air Force agreed to take up the balance of the French order which was diverted to the UK and the bombers were given the service name "Boston", with the further designation of "
Mark I" or "Mark II" according to the earlier or later engine type. ;Havoc Mk I: The Boston was generally considered unsuitable for use by the RAF since its range was too limited for daylight raids on Germany. Many of the Boston Mk II, plus some re-engined Mk Is, were converted for nighttime duties – either as intruders with 2,400 lb (1,100 kg) of bombs, or as night fighters with
AI Mk. IV radar. These
Havoc Mk I aircraft were found to be under-powered and were replaced by the
de Havilland Mosquito. A total of 181 Bostons were converted to Havocs. In
interdiction raids, Havoc intruders caused considerable damage to German targets. ;Havoc-Pandora: Twenty Havocs were converted into "intruder" aircraft, carrying the Long Aerial Mine (LAM), an explosive charge trailed on a long cable in the path of enemy aircraft in the hope of scoring a hit. Trials conducted with a single
Handley Page Harrows dropping LAMs into the stream of German bombers were not successful, and the Havocs were converted back to Mk I intruders. ;Havoc I
Turbinlite :Havoc I fitted with a 2.7 million
candlepower searchlight in the nose; the batteries for it carried in the bomb bay. A radar operator sat in the after fuselage. They were unarmed, and they were supposed to illuminate targets for accompanying
Hawker Hurricane fighters. A total of 31 aircraft were converted. They were made obsolete by high performance fighters that could carry their own radar. ;DB-7/Havoc I :Initial French variant, fitted with two Pratt & Whitney R-1830. Of the 270 DB-7s ordered 116 were accepted by the French before the armistice. ;DB-7A/Havoc II :The French Purchasing Commission ordered 100 more bombers, to be fitted with Wright R-2600-A5B Twin Cyclone engines, the same basic engine design as used by
North American Aviation's contemporary
B-25 medium bomber. These DB-7 aircraft were designated as the
DB-7A by Douglas Aircraft. None of these were delivered before the fall of France and they were sent to the UK instead. These were converted into night fighters, by the addition of 12 0.303 inch machine guns in their noses and extra fuel tanks. They had a top speed of 344 mph (550 km/h) at higher altitudes. A total of 39 aircraft were used briefly as Turbinlites. ;DB-7B/Boston III: The
DB-7B was the first batch of this model to be
ordered directly for the Royal Air Force. This was done in February 1940. These were powered by the same engines as the DB-7A, with better
armor protection. Importantly, these had larger fuel tanks and they were suitable for use by the RAF as light bombers. This was the batch for which the name "Boston" was first assigned but since the DB-7s intended for France entered service in the RAF first, the aircraft in this order were called the
Boston Mk III. Among other combat missions, they took part in the attacks on the German warships
Scharnhorst,
Gneisenau and
Prinz Eugen during their
dash through the English Channel (Operation Cerberus) and the
raid on Dieppe ("Operation Jubilee"). Three hundred Boston III were produced and delivered and some of them were converted for use as night fighters. ;DB-73: A variation on the DB-7B/Boston III built for a French government order and featuring French instruments and secondary equipment; of the 480 DB-73s ordered by France, 240 were built by under license by the
Boeing Company in Seattle. None were delivered, due to the
fall of France, the DB-73 block was ordered by the RAF, after conversion to the Boston III configuration. Following the
German invasion of the Soviet Union, 151 DB-73s were provided to the USSR. Following the Japanese
Attack on Pearl Harbor, a further 356 DB-73s were taken up by the USAAF, which transferred 22 to the
Royal Australian Air Force (RAAF) for use in the
South West Pacific theatre. Australian sources usually list these aircraft as DB-7B. s, which were also carried (one-only under each wing) by
Republic P-47 Thunderbolts. :When shipments to the UK finally resumed, they were delivered under the terms of the Lend-Lease program. These aircraft were actually refitted A-20Cs known as the
Boston IIIA. ;A-20: The original American indifference to the Model 7B was overcome by the improvements made for the French and British, and the United States Army Air Corps ordered two models, the
A-20 for high-altitude bombing and the
A-20A for low and medium altitude combat. Both were similar to the DB-7B. The A-20 was to be fitted with
turbosupercharged Wright R-2600-7 engines, but these were bulky and the prototype suffered cooling problems, so the remainder were completed with the two-stage supercharged R-2600-11, 59 as
P-70 fighters and 3 as
F-3 reconnaissance aircraft. One A-20 was evaluated by the U.S. Navy as the
BD-1, while the
U.S. Marine Corps flew eight as the
BD-2. ;A-20A: The U.S. Army ordered 123 A-20As with R-2600-3 engines, and 20 more with the more powerful R-2600-11. They entered service in the spring 1941. The Army liked the A-20A because of its good performance and because it had no adverse handling characteristics. Nine of them were transferred to the RAAF in 1943. The USAAF used the British name Havoc for the A-20A, while the RAAF referred to them as Bostons. ;A-20B: The
A-20B received the first significant order from the Army Air Corps: 999 aircraft. These resembled the DB-7A rather than the DB-7B, lacking self sealing fuel tanks, with light armor and stepped rather than slanted glazing in their noses. In practice, 665 of these were exported to the
Soviet Union, so only about one third of them served with the USAAF. ;A-20C: The
A-20C was an attempt to develop a standard, international version of the DB-7/A-20/Boston, produced from 1941. It reverted to the slanting nose glass, and it had RF-2600-23 engines,
self-sealing fuel tanks, and additional protective armor. These were equipped to carry an external
aerial torpedo. A total of 948 were built for Britain and the Soviet Union, but many were retained by the USAAF after the Japanese attack on Pearl Harbor. The Soviet A-20s were often fitted out with turrets of indigenous design. ;A-20D: Proposed lightweight version with R-2600-7 engines and non-self-sealing fuel tanks. Unbuilt. ;A-20G: The
A-20G, delivered from February 1943, would be the most produced A-20 variant, with 2,850 built. The glazed nose was replaced by a solid nose containing four 20 mm (.79 in)
Hispano cannon and two .50 in
M2 Browning machine guns. After the first batch of 250, the less-accurate cannon were replaced by more machine guns. After 750 aircraft had been built, a power-driven gun turret fitted with two .50 in machine guns was fitted, with the fuselage wider as a result, and the ventral tunnel gun changed from a .30 in to another .50 in Browning. The powerplants were two R-2600-23. Many A-20Gs were delivered to the Soviet Union. Notably, U.S. A-20Gs were used on low-level sorties in the
New Guinea campaign. ;A-20H: The
A-20H was the same as A-20G, continued with the 1,700 hp (1,270 kW) R-2600-29. 412 of these were built. The takeoff weight was raised to . ;ZB-20H: In 1948, the last surviving A-20H in United States service was redesignated "B-20" with the elimination of the "A for Attack" category, and was given the "Z" prefix as being obsolete. ;A-20J/Boston IV: The
A-20J carried an additional bombardier in an extended
acrylic glass nose section. These were intended to lead bombing formations, with the following standard A-20s dropping their bombs when signaled by the leader. A total of 450 were built, 169 for the RAF which designated them Boston Mk IV from the summer of 1944 onwards. ;A-20K/Boston V: The
A-20K (Boston Mk V in RAF parlance) was the final production version of the A-20 series, the same as the A-20J except for R-2600-29s instead of -23s. ;P-70: In October 1940, the USAAC felt a need for long-range fighters more than attack bombers. As a result, sixty of the production run of A-20s were converted to P-70 night fighters, all delivered by September 1942. They were equipped with SCR-540 radar (a copy of the British AI Mk IV), the glazed nose often being painted black to reduce glare and hide the details of the radar set, and had four 20 mm (.79 in) forward-firing cannon, each provided with 120 rounds, in a tray in the lower part of the bomb bay, while the upper part held an additional fuel tank with a capacity of . In 1943, between June and October, 13 A-20Cs and 51 A-20Gs were converted to
P-70A. Differences were to be found in the armament, with the 20mm cannon package replaced by an A-20G gun nose with six .50 caliber guns installed, the SCR-540 radar installation being carried in the bomb bay with the vertical-plane, twin-dipole "arrowhead" transceiving antenna protruding between the nose guns. Further P-70 variants were produced from A-20G and J variants. The singular airframe
P-70B-1 (converted from an A-20G) and subsequent
P-70B-2s (converted from A-20Gs and Js) had American centimetric radar (SCR-720 or SCR-729) fitted. The P-70s and P-70As saw combat only in the Pacific during World War II and only with the USAAF. The P-70B-1 and P-70B-2 aircraft never saw combat but served as night fighter aircrew trainers in the US in Florida and later in California. All P-70s were retired from service by 1945. ;F-3A: The F-3A was a conversion of forty-six A-20J and K models for night-time photographic reconnaissance (F-3 were three conversions of the original A-20). This variant was employed in the European Theater by the 155th Photo Reconnaissance Squadron which began its deployment as the 423rd Night Fighter Squadron. The 423rd was converted to its photo mission as the 155th Photo Reconnaissance Squadron in part because of knowledge of night fighter tactics which could be used to defend against German aircraft. Although the armament was removed, the crew of three was retained, consisting of a pilot, observer, and navigator. The first Allied aircraft to land at Itazuke, Japan after the August 1945 surrender was an F-3A. ;BD-1 :One A-20A was bought in 1940 by the United States Navy for evaluation for use by the United States Marine Corps. The Navy/Marine Corps did not have any priority on the production lines, so the BD was not put into service. ;BD-2 :In 1942, eight former Army A-20Bs were diverted to the United States Navy for use as high-speed target tugs. Despite the addition of the target-towing equipment and the removal of all armament and the provision to carry bombs, the aircraft were still designated
BD in the Bomber sequence. They were withdrawn from service in 1946. ;O-53 :An observation/reconnaissance version of the A-20B powered by two R-2600-7 engines. The original order for 1,489 aircraft was canceled and none were built. == Operators ==