It was one of three twin-engined, front line medium bomber types that were in service with the Royal Air Force (RAF) at the outbreak of the Second World War.

Alongside the Vickers Wellington and the Handley Page Hampden, the Whitley was developed during the mid-1930s according to Air Ministry Specification B.3/34, which it was subsequently selected to meet.

Following the outbreak of war in September 1939, the Whitley participated in the first RAF bombing raid upon German territory and remained an integral part of the early British bomber offensive.

[2] Its front-line service included maritime reconnaissance with Coastal Command and the second line roles of glider-tug, trainer and transport aircraft.

In July 1934, the Air Ministry issued Specification B.3/34, seeking a heavy night bomber/troop transport to replace the Handley Page Heyford biplane bomber.

[3] This combination bomber/transport was part of the RAF's concept of fighting wars in distant British Empire locations, where the aircraft would fly into the theatre of action carrying troops and then provide air support.

[3] Lloyd selected the Armstrong Siddeley Tiger IX radial engine to power the Whitley, which was capable of generating 795 hp (593 kW).

[3] According to aviation author Philip Moyes, the decision to adopt the semi-monocoque fuselage was a significant advance in design; many Whitleys surviving severe damage on operations.

The ventral turret was hydraulically-powered but proved to be hard to operate and added considerable drag, thus the Whitley Mk III was the only variant with it.

[12] The decision was made to introduce a series of other minor improvements to produce the Whitley Mk V. These included the modification of the tail fins and rudders, the fitting of leading edge de-icers, further fuel capacity increases, a smaller D/F loop in a streamlined fairing being adopted, and the extension of the rear fuselage by 15 in (381 mm) to improve the rear-gunner's field of fire.

Unlike the other variants, it was developed for service with RAF Coastal Command and was thus furnished for maritime reconnaissance rather than as a general purpose bomber.

[13] It had a sixth crew member to operate the new ASV Mk II radar system along with an increased fuel capacity for long endurance anti-shipping missions.

[4] The Whitley featured a large rectangular-shaped wing; its appearance led to the aircraft receiving the nickname "the flying barn door".

[17] The forward surfaces of the wings were composed of flush-riveted, smooth and unstressed metal sheeting; the rear 2/3rds aft of the box spar to the trailing edge, as well as the ailerons and split flaps was fabric covered.

[4] The tailplanes employed a similar construction to that of the wings, the fins being braced to the fuselage using metal struts; the elevators and rudders incorporated servo-balancing trim tabs.

[19] Alongside the Handley Page Hampden and the Vickers Wellington, the Whitley bore the brunt of the early fighting and saw action during the first night of the war, when they dropped propaganda leaflets over Germany.

[22] On the night of 19/20 March 1940, in conjunction with Hampdens, the Whitley conducted the first bombing raid on German soil, attacking the Hörnum seaplane base on the Island of Sylt.

[19] Unlike the Hampden and Wellington, which had met Specification B.9/32 for a day bomber, the Whitley was always intended for night operations and escaped the early heavy losses received during daylight raids carried out upon German shipping.

Whitleys flew a total of 8,996 operations with Bomber Command, dropped 9,845 tons (8,931 tonnes) of bombs and 269 aircraft were lost in action.

[21][23] Many leading World War II bomber pilots of the RAF flew Whitleys at some point in their career, including Don Bennett, James Tait, and Leonard Cheshire.

If this was not timed correctly the airflow would drag the paratrooper out resulting in nasty injuries to the face against the lip of the chute known as a Whitley kiss.

The type continued to operate delivering supplies and agents in the Special Duties squadrons (138 and 161) until December 1942, as well as serving as a transport for troops and freight, a carrier for paratroopers and a tow aircraft for gliders.

[26] The first U-boat kill attributed to the Whitley Mk VII was the sinking of the German submarine U-751 on 17 July 1942, which was achieved in combination with a Lancaster heavy bomber.

[28][29] Having evaluated the Whitley in 1942, the Fleet Air Arm operated a number of modified ex-RAF Mk VIIs from 1944 to 1946, to train aircrew in Merlin engine management and fuel transfer procedures.

The conversion process involved the removal of all armaments, the turret recesses were faired over, additional fuel tanks were installed in the bomb bay, the interior of the fuselage was adapted for freight stowage, and at least one aircraft was fitted with an enlarged cargo door.