<P> On the British side, three bomber types were mostly used on night operations against targets such as factories, invasion ports and railway centres; the Armstrong Whitworth Whitley, the Handley - Page Hampden and the Vickers Wellington were classified as heavy bombers by the RAF, although the Hampden was a medium bomber comparable to the He 111 . The twin - engined Bristol Blenheim and the obsolescent single - engined Fairey Battle were both light bombers; the Blenheim was the most numerous of the aircraft equipping RAF Bomber Command and was used in attacks against shipping, ports, airfields and factories on the continent by day and by night . The Fairey Battle squadrons, which had suffered heavy losses in daylight attacks during the Battle of France, were brought up to strength with reserve aircraft and continued to operate at night in attacks against the invasion ports, until the Battle was withdrawn from UK front line service in October 1940 . </P> <P> Before the war, the RAF's processes for selecting potential candidates were opened to men of all social classes through the creation in 1936 of the RAF Volunteer Reserve, which "...was designed to appeal, to...young men...without any class distinctions ..." The older squadrons of the Royal Auxiliary Air Force did retain some of their upper - class exclusiveness, but their numbers were soon swamped by the newcomers of the RAFVR; by 1 September 1939, 6,646 pilots had been trained through the RAFVR . </P> <P> By summer 1940, there were about 9,000 pilots in the RAF to man about 5,000 aircraft, most of which were bombers . Fighter Command was never short of pilots, but the problem of finding sufficient numbers of fully trained fighter pilots became acute by mid-August 1940 . With aircraft production running at 300 planes each week, only 200 pilots were trained in the same period . In addition, more pilots were allocated to squadrons than there were aircraft, as this allowed squadrons to maintain operational strength despite casualties and still provide for pilot leave . Another factor was that only about 30% of the 9,000 pilots were assigned to operational squadrons; 20% of the pilots were involved in conducting pilot training, and a further 20% were undergoing further instruction, like those offered in Canada and in Southern Rhodesia to the Commonwealth trainees, although already qualified . The rest were assigned to staff positions, since RAF policy dictated that only pilots could make many staff and operational command decisions, even in engineering matters . At the height of fighting, and despite Churchill's insistence, only 30 pilots were released to the front line from administrative duties . </P> <P> For these reasons, and the permanent loss of 435 pilots during the Battle of France alone along with many more wounded, and others lost in Norway, the RAF had fewer experienced pilots at the start of the initial defence of their home . It was the lack of trained pilots in the fighting squadrons, rather than the lack of aircraft, that became the greatest concern for Air Chief Marshal Hugh Dowding, Commander of Fighter Command . Drawing from regular RAF forces, the Auxiliary Air Force and the Volunteer Reserve, the British were able to muster some 1,103 fighter pilots on 1 July . Replacement pilots, with little flight training and often no gunnery training, suffered high casualty rates, thus exacerbating the problem . </P>

A major reason for the british victory in the battle of britain was