Volvo Aero is a supplier of single-engine systems for military aircraft. These have largely been in partnership with other engine manufacturers, such as the RM1 (de Havilland Goblin) for the Saab 21R, RM2 (de Havilland Ghost) for the Saab J29, RM5 and RM6 (Rolls-Royce Avon) for the Saab 32 Lansen, the RM6B for the Saab 35 Draken, and the RM8 (Pratt & Whitney JT8D) for the Saab 37 Viggen. The Saab JAS 39 Gripen's RM12 engine is a derivative of the General Electric F404.