Per Air Force Instruction 36–2618, master sergeants do serve in positions as squadron superintendents, flight chiefs, section chiefs, and Noncommissioned Officer in Charge (NCOIC). Master sergeants are the lowest pay grade in the Air Force and Space Force at which one can hold the special duty position and responsibilities of a first sergeant. Air Force first sergeants occupy the pay grades of E-7 through E-9 and are referred to officially as "first sergeant" regardless of pay grade, and unofficially as "first shirt" or "shirt".