Final assembly of all Austin-built Stirlings and, later, Lancasters was done at Marston Green, where a new factory, Aero Works Frames, was constructed in 1940. Fuselages, wings and so forth were transported by road on Ministry of Aircraft Production trailers. The journey between Austin’s East Works and Marston Green — about 15 miles — required the removal of various pieces of street furniture and, in one case, the cutting of a roadway through a traffic island.
Test-flying of completed aircraft from the Marston Green factory was conducted from Birmingham’s Elmdon aerodrome, which was requisitioned by the government in early 1941. The grass runway was unsuitable for heavy aircraft and a hard-core was laid. This broke up under the weight of the Stirlings and, after some lobbying by the Austin test pilots, was replaced by concrete. It was also necessary to build a concrete track which stretched from the factory to Elmdon’s hangars. Aircraft were towed from the assembly plant, across the LMS (London Midland & Scottish) railway line, via a temporary bridge to the airfield. There, new hangars were constructed for pre-flight testing. Once the test pilots were satisfied, aircraft were delivered to maintenance units. Some 620 Stirlings and 330 Lancasters were produced in this fashion.