In July 1934, Air Ministry approached Vickers, Fairey, Handley Page and Armstrong Whitworth with requirements B.3/34 for a monoplane, twin-engine, night heavy bomber that could also serve as a transport aircraft. However, it turned out that the price offered by AM for the prototypes developed from scratch did not suit any of the companies. In this situation, the Ministry took advantage of the fact that Vickers and Armstrong Whitworth were already working on interesting aircraft designs and in August proposed modifying them accordingly. Vickers developed an enlarged version of its design for B.9/32 (later ‘Wellington’). In turn, the W. G. Armstrong Whitworth Aircraft Co. developed the following designs: A.W.23 - transport plane for C.26/31 and, by order of the Czech government, a bomber plane A.W.30. The latter project interested AM. The chief designer of the factory, John Lloyd, proposed the project A.W.38, which was a combination of parts of both projects: the fuselage of A.W.30 and the wings of A.W.23. On 14.09.1934 AM ordered 2 prototypes, demanding a very fast progress of works, as well as the maximum technological simplification of the construction, allowing to shorten the production process. The project used the construction solutions that were innovative for those times: caisson structure of the airframes and monocoque fuselage. It was also the first British heavy bomber with a retractable undercarriage. To simplify the production the airframe components were reduced to a minimum and standardized to the maximum. The engines of the type Armstrong Siddeley Tiger IX were chosen for the propulsion units. The work on prototypes A.W.38 proceeded very fast. Already in December 1934 a mock-up of the plane was ready. On 23.08.1935, long before the first flight of the prototype, the contract for the delivery of 80 copies of the new plane was signed. The prototype A.W.38 was flown on 17.03.1936. The airplane, although it had higher performance than the heavy bombers RAF at that time, it did not meet the requirements. However, due to the great needs of the RAF, in May 1936 RAF ordered 240 more examples. The second prototype was flown on 11.02.1937. It received Armstrong Siddeley Tiger XI engines, in accordance with the new B.21/35. On 30.08.1937. it crashed on the airfield of the research center in Farnborough. The first serial Mk I was flown on 23.12.1936. The first planes were delivered to No. 10 Squadron RAF. At the end of June 1937, the squadron was fully rearmed and became part of the 4th Bomb Group. It later became a formation armed exclusively with the Whitleys, and all versions of the aircraft passed through its squadrons. In 1937. Whitleys received the 58 and 78 Squadrons. The planes of the Mk I version were delivered between 03.1937 and 01.1938. It soon became obvious that the new aircraft required improvements, especially in maximum speed and range. Therefore new engines with higher power and two-stage supercharger were used. The prototype, the world’s first military aircraft with engines with such superchargers, was flown on 8.12.1937, thus creating the Mk II, which entered service with RAF Squadrons (7, 51 and 58) in January 1938. Aircrafts of the Mk II version were delivered between 01. and 06.1938. Four aircrafts of this version were the first to be used for training British paratroopers in the center, later known as the Parachute School, established in Ringway in 1940.

For the requirements B.20/36, issued in August 1936, Mk III version was developed, which differed from the Mk II in armament. The manually rotated nose turret was replaced by a hydraulically driven turret, and an additional retractable dustbin turret. The prototype took off for the first time on 14.03.1938. The first serial Mk III flew on 7.09.1938 and shortly afterwards they started service in 51, 77 and 102 Bomber Squadrons. Planes of the Mk III version were delivered between 08.1938 and 02.1939. Since 1936, work began on another version of bomber powered by Rolls Royce Merlin II engines. The prototype of the new version was flown on February 11, 1938. The successful course of trials led to the decision to produce aircraft Mk IV equipped with Merlin. The first serial plane made its first flight on 18.04.1938. Merlin brought significant improvement of performance of the plane. Seven last planes of this version were equipped with ‘Merlin X’ engines with higher horsepower. They were designated Mk IVA. The defensive armament was also seriously strengthened by installing a hydraulically driven turret with four 7.7 mm machine guns in the tail. At the time this was an armament of fantastic parameters Whitley Mk IV became the first aircraft in the world with such a powerful armament. Mk IV entered service with the RAF in May 1939, with 10 Squadron. Later it was also transferred to 78 Squadron (4th Group). Mk IV version aircraft were delivered between May and August 1939. On 4.08.1939 a prototype of improved version Mk V with fuselage lengthened by 15 inches behind the tail, the extension resulting in an increase in the field of fire for the rear guns, was flown. RAF began receiving new aircraft a month before the outbreak of war. First examples were delivered to 78 Squadron in August 1939. 78 Squadron. The planes of Mk V version were delivered from August 1939. 1466 of them were produced. The last one, took off for the first time on 8.06.1943 and remained in the company, which it served as a glider tug in the flying wing configuration, AW 52G. This aircraft was withdrawn from service in December 1948. Aircrafts of this version were mainly used as glider tugs (since 1941). The glider being towed was usually a Horsa. The Mk VI version remained only in the design stage. It was to be powered Pratt & Whitney G.R.1830 Twin Wasp, which were intended to be used in the event of possible restrictions on the supply of Merlins. It never happened, and the assurance turned out to be unnecessary. The demonstrated usefulness of the Whitley in 1939-40 as a maritime patrol aircraft resulted in the creation of the GR Mk VII version. Designated by the factory as the Type 217 version, it was ordered in late 1940. Its prototype was the result of an adaptation of one of the Mk V version aircraft, which involved fitting it with ASY Mark II long-range radar (as the first RAF aircraft) and increasing its fuel reserve. The crew was increased by the radar operator, to six members. A number of older Mk V aircraft were converted to GR Mk VII. Some of the GR Mk VII were used as training aircraft for radar operators. Mk VII planes were delivered from July 1941, in small series as part of Mk V production. The last one was delivered on 9.12.1942. Some Mk VII’s were converted into aircraft for on-board mechanics training.

In April-May 1942 15 planes of Mk V version were converted into transporters for BOAC airlines, removing armament from planes and adapting fuselage interior for cargo carrying. They were used for flights from Great Britain to West Africa, from Gibraltar to Malta and on the Scotland-Stockholm route. They returned to the RAF in 1943. Several aircraft were used for various trials and tests. In late 1938, newly developed Armstrong Siddeley Deerhound engines were installed on one of the Mk II version aircraft. The plane was flown on 6.01.1939. Unfortunately on 6.03.1940 it crashed, burying all on board. It resulted in the abandonment of further development of the project.

In total, Armstrong Whitworth produced 2 prototypes, 34 Mk I, 46 Mk II, 80 Mk III, 40 Mk IV, 1466 Mk V and 146 Mk VII. Deliveries to the RAF were discontinued on 6 June 1943.

At the time of Britain’s declaration of war on Germany, 3.09.1939, the British Bomber Air Force had 196 Whitleys. During the odd war the Whitleys dropped leaflets, on 1/10/1939 three Mk IV’s dropped leaflets over Berlin as the first British aircraft to appear over the capital of the Third Reich. Propaganda purposes were also served by flights over Prague and Warsaw. It was not until the night of 19/20.03.1940 that the planes dropped their first bombs on German territory, attacking the seaplane base on the Sylt Island. On the night of 10/11.05.1940. Whitleys bombed for the first time the continental territory of Germany. On the night of 11/12.06.1940. they made the first air raid on the targets in Italy. On the night of 25/26.08.1940. Whitleys were in a formation of RAF bombers, which bombed Berlin for the first time. After that, they bombed almost all important targets in Germany, carried out raids over Austria, Poland and Czech Republic. The last raid with their participation was the attack on Ostend on 29.04.1942. After that date, they were withdrawn from Bomber Command, although planes from OTU still participated in some of the first raids of the „Thousand-bomber raids”.

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