The prototype Wellington made its first flight on 15 June 1936, but it was not until October 1938 that production aircraft began to enter RAF service. Less than one year later (on 4 September 1939) Wellingtons were in action against targets in Germany. Early deployment on daylight raids showed that these and other British bomber aircraft were extremely vulnerable to fighter attack. Following the loss of ten Wellingtons from a force of 24 despatched on an armed reconnaissance of Wilhelmshaven on 18 December 1939, the type was withdrawn from daylight operations. As a night bomber, however, the Wellington proved an invaluable weapon during the early years of Bomber Command's offensive against Germany.
Wellington production was to total 11,461 aircraft and embraced many versions.