U.S. Armed Services not to do so. The Air Force inherited warrant officer ranks from the Army at its inception in 1947. The Air Force stopped appointing warrant officers in 1959, the same year the first promotions were made to the new top enlisted grade, Chief Master Sergeant. Most of the existing Air Force warrant officers entered the commissioned officer ranks during the 1960s, but small numbers continued to exist in the warrant officer grades for the next 21 years. The last active duty Air Force warrant officer, CWO4 James H. Long, retired in 1980 and the last Air Force Reserve warrant officer, CWO4 Bob Barrow, retired in 1992. Upon his retirement, he was honorarily promoted to CWO5, the only person in the Air Force ever to hold this grade. Since Barrow's retirement, the Air Force warrant officer ranks, while still authorized by law, are not used. Enlisted airmen Enlisted airmen have pay grades from E-1 (entry level) to E-9 (senior enlisted). While all USAF personnel, enlisted and officer, are referred to as airmen, in the same manner that all Army personnel, enlisted and officer, are referred to as soldiers, the term also refers 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 (i.e., pay grades E-5 through E-9) all ranks fall into the category of NCO and are further subdivided into "NCOs" (pay grades E-5 and E-6) and "senior NCOs" (pay grades E-7 through E-9); the term "junior NCO" is sometimes used to refer to staff sergeants and technical sergeants (pay grades E-5 and E-6). The USAF is the only branch of the U.S. military where NCO status is achieved when an enlisted person reaches the pay grade of E-5. In all other branches, NCO status is generally achieved at the pay grade of E-4 (e.g., a corporal in the Army and Marine Corps, Petty Officer Third Class in the Navy and Coast Guard). The Air Force mirrored the Army from 1976 to 1991 with an E-4 being either a senior airman wearing three stripes without a star or a sergeant (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 according to the AFI 36–2618. Uniforms The