Adolf Busemann had proposed swept wings as early as 1935; Messerschmitt researched the topic from 1940. In April 1941, Busemann proposed fitting a 35° swept wing ("Pfeilflügel II", literally "arrow wing II") to the Me 262, the same wing-sweep angle later used on both the American F-86 Sabre and Soviet Mikoyan-Gurevich MiG-15 fighter jets. Though this was not implemented, he continued with the projected HG II and HG III ("Hochgeschwindigkeit", "high-speed") derivatives in 1944, designed with a 35° and 45° wing sweep, respectively.