The Dornier Do 335 Pfeil ("Arrow") was a World War II heavy fighter built by the Dornier company. The Pfeil's performance was much better than other twin-engine designs due to its unique push-pull configuration and the lower aerodynamic drag of the in-line alignment of the two engines. It was Nazi Germany's fastest piston-engined aircraft of World War II. The Luftwaffe was desperate to get the design into operational use, but delays in engine deliveries meant that only a handful were delivered before the war ended. When the US Army overran the Oberpfaffenhofen factory in late April 1945, only 11 Do 335A-1 single seat fighter-bombers and two Do 335A-12 conversion trainers had been completed. As part of Operation Seahorse, two of the surviving A-0 single seaters were put aboard the US aircraft carrier 'Reaper' and shipped back to the USA, for detailed evaluation by the US Navy and USAAF. An airworthy A-12 two seater was flown to Britain and flight tested at RAE Farnborough, but a companion A-1 force-landed in France on its delivery flight and was abandoned.