Senior master sergeant Senior master sergeant ( SMSgt ) is the eighth enlisted rank ( pay grade E - 8 ) in the U . S . Air Force , just above master sergeant and below chief master sergeant and is a senior noncommissioned officer ( SNCO ) . According to Air Force Instruction 36 - 2618 , " The Enlisted Force Structure " : SMSgts are key , experienced , operational leaders , skilled at merging their personnel ' s talents , skills , and resources with other teams ' functions to most effectively accomplish the mission . SMSgts continue to develop their leadership and management skills in preparation for expanded responsibilities and higher leadership positions . SMSgts normally operate at the operational level of leadership . Promotion to senior master sergeant is the most difficult enlisted promotion to attain in the Air Force . It is the first enlisted grade to which results of a central promotion board are the primary factor in selection for promotion . Usually , less than ten percent of eligible master sergeants are selected for promotion to senior master sergeant in most years . Selectees typically have vast technical and leadership experience gained from a broad variety of assignments at both line and staff functions throughout their careers . Additionally , the successful candidate will typically have completed an associate ' s or bachelor ' s degree in their Air Force specialty as well as the Senior Noncommissioned Officer Correspondence Course and have had their latest performance report endorsed by a senior rater , usually a colonel or brigadier general . Senior master sergeants typically assume superintendent duties , overseeing enlisted members ' efforts to accomplish a major segment of a unit ' s mission , in preparation for promotion to the rank of chief master sergeant . They are expected to serve as mentors for noncommissioned and junior commissioned officers . Senior master sergeants in the first sergeant special duty serve as first sergeants of larger units than those employing master sergeants as first sergeants . These first sergeants ( pay grades E - 7 to E - 9 ) are referred to officially as " First Sergeant " ( regardless of their pay grade ) , and unofficially as " First Shirt " or simply " Shirt " . Public Law 107 - 107 , the " National Defense Authorization Act " , establishes senior enlisted strength levels for all branches of the US military . Currently , only 2 . 5 percent of the Air Force ' s total active duty enlisted strength may hold this rank . Senior master sergeants are sometimes casually referred to by the nickname of " Senior " . The official terms of address are " Senior Master Sergeant " and " Sergeant " per Air Force Instruction 36 - 2618 . Historical note . Although the Air Force had been an independent service since 1947 , the rank of senior master sergeant did not come into being until the authorization of the Military Pay Act of 1958 . This act established the pay grades of E - 8 and E - 9 but without title . It wasn ' t until late 1958 that the title of senior master sergeant ( and the accompanying rank insignia ) was decided upon after the enlisted force was polled . At that time , the senior master sergeant rank had only a single chevron above and six below , and a chief two above and six below . In 1991 the Air Force changed its NCO insignia so that a maximum of five stripes were placed on the bottom of the chevrons , adding one above to each of the top three grades , resulting in the present form .