Oberstabsfeldwebel (OStFw or OSF) is the highest Non-commissioned officer (NCO) rank in German Army and German Air Force. It is grouped as OR9 in NATO, equivalent to a Sergeant Major in the United States Army / Chief Master Sergeant (United States Air Force), and a Warrant Officer Class 1 in the British Army / Warrant officer (Royal Air Force). Attainment of this rank requires at least sixteen years since promotion to feldwebel and at least six years since promotion to hauptfeldwebel[1]