<P> While all Air Force military personnel are referred to as Airmen, it can specifically refer to the pay grades of E-1 through E-4 which are below the level of non-commissioned officers (NCOs). Above the pay grade of E-4 (E-5 through E-9) all ranks fall into the category of NCO and are further subdivided into NCOs (E-5 & E-6) and Senior NCOs (E-7 through E-9); the term Junior NCO is sometimes used to refer to staff sergeants and technical sergeants (E-5 & E-6). </P> <P> The Air Force is the only one of the five branches of the United States military where NCO status is now only achieved at the grade of E-5 . Formerly, the grade of Sergeant was obtained after a time as a Senior Airman and successful completion of the Air Force NCO School . In all other branches, NCO status can be achieved at the grade of E-4 (a Corporal in the Army and Marine Corps, Petty Officer Third Class in the Navy and Coast Guard). However, E-4s in the Army with the rank of Specialist are not NCOs . The Air Force mirrored the Army from 1976 to 2 May 1991 with an E-4 being either a Senior Airman wearing three stripes without a star or a Sergeant (informally referred to as "Buck Sergeant") which was noted by the presence of the central star and considered an NCO . Despite not being an NCO, a Senior Airman who has completed Airman Leadership School can be a supervisor . </P> <P> Although the Air Force became an independent service with the National Security Act of 1947, it retained the Army Air Force rank structure and corresponding insignia of years past . This rank structure provided for seven enlisted ranks: Private, Private First Class, Corporal / Technician Fifth Grade, Sergeant / Technician Fourth Grade, Staff Sergeant / Technician Third Grade, Technical Sergeant and Master Sergeant / First Sergeant . Additionally, Air Force personnel were still referred to as soldiers . During the Second World War, many USAAF NCOs wore the Army Air Corps branch insignia of the winged propeller underneath their chevrons . </P> <P> Changes to the rank structure were proposed almost immediately but did not start occurring until the next year . Sometime during late 1947 and early 1948, new chevron designs were tested at Bolling Air Force Base . The style preferred was the one used today, the inverted chevron . Air Force Chief of Staff General Hoyt Vandenberg approved the new chevron on 9 March 1948 . A new Air Force "Uxbridge Blue" uniform and black leather replaced the US Army Air Corps Olive Drab uniform and russet leather in 1949 . Air Force personnel were allowed to wear their old Army World War Two pattern uniforms and rank insignia until July, 1952 . Recolored "hash marks" and Overseas Service Bars were worn on the uniform until 1957 . </P>

What is a sergeant in the air force