 The Bf 109E escorts had a limited fuel capacity resulting in only a 660 km (410 mile) maximum range solely on internal fuel, and when they arrived over a British target, had only 10 minutes of flying time before turning for home, leaving the bombers undefended by fighter escorts.Its eventual stablemate, the Focke-Wulf Fw 190A, was only flying in prototype form in the summer of 1940; the first 28 Fw 190A-0 service test examples were not delivered until November 1940.The Fw 190A-1 had a maximum range of 940 km (584 miles) on internal fuel, 40% greater than the Bf 109E.