on trucks to Keevil Airfield. In a hangar at Keevil the Spitfire would be assembled, tested and then flown by an ATA (Air Transport Auxiliary) pilot to a frontline airfield. Often there were also conflicts with other Ministries, who had already requisitioned sites needed by Supermarine, but the Ministry for Aircraft Production usually ruled supreme as the production of aircraft had the highest priority. Production fell from 363 aircraft in the quarter before the raids to 177 and 179 respectively in the next two quarters. It took another nine months before it was back to 100 per month, as the programme both had to find suitable new facilities, sufficient skilled workers to replace those killed and wounded and also the additional numbers needed to increase production, while at the same time provide accommodation for them. There was a great reluctance of Southampton-based workers to move away to the new dispersal facilities. Once the existing skilled workers were relocated it took time to train new semi-skilled workers. Many were straight out of school or older men who had undergone the Government's basic engineering training. As the war progressed more woman entered the workforce and began to take on more senior roles. By the end of the war, 8,000 planes had been built in the dispersal factories around Southampton. In addition to the Spitfires and Seafires made at Supermarine's dispersed Southampton factories and at Castle Bromwich, several companies were subcontracted to make entire Supermarine designs. The most significant were Westland Aircraft who were responsible for the manufacture of the majority of the Seafire, making over 2,000, while Cunliffe-Owen Aircraft at their shadow factory at Eastleigh from 1942 converted 118 Spitfires VBs into Seafires before constructing over 520 new Seafires. New designs Joe Smith was confident that the Spitfire had great development potential and was successful in obtaining the maximum capability from the Spitfire and its naval version the Seafire through numerous variants, including the introduction of the Rolls-Royce Griffon-engined series, all of which ensured that it remained a front line fighter until the end of World War II. By 1942, the designers had realised that the characteristics of the Spitfire's wing at high Mach numbers might become a limiting factor in further increasing the aircraft's high-speed performance. As a result, work commenced on the Spiteful and Seafang, which were designed to be successors of the Spitfire and Seafire, respectively. However, with the