Under officer Under officer is an appointment held by senior cadet s at some Commonwealth officer training establishments and in University Officers ' Training Corps in the United Kingdom , and also a rank used in some Commonwealth cadet forces . Australia . The Royal Military College , Duntroon uses the appointments of senior under officer and under officer for senior Staff Cadet s . In the Australian Army Cadets and Australian Air Force Cadets , the rank of cadet under officer is the highest cadet rank . They are saluted and addressed as " Sir " or " Ma ' am " by their subordinates but not by adult officers or instructors or members of the Australian Defence Force . AAC cadet under officers may be assigned as national , regional , or battalion under officer , as quartermaster , or as the commander of a company or platoon . The rank badge is a lozenge , which contains 27½ chevron s . The national cadet under officer has red in the centre of the lozenge . Regional cadet under officers have blue in the centre of the lozenge . To become a cadet under officer , a cadet must have completed the senior leaders course module two , otherwise known as the CUO / WO course , often held either at a mid or end of year session . The course runs for one week on a military base , and during this course a prospective cadet under officer will learn platoon and company level command . To gain entry to the course the cadet must have successfully completed the senior leaders course module one or the sergeant course , which entitles them to bear ranks up to staff sergeant . The insignia for an Australian Air Force Cadet ( AAFC ) cadet under officer is a thick white stripe . To achieve the rank of cadet under officer , an AAFC cadet sergeant , cadet flight sergeant or cadet warrant officer must complete the cadet under officer course , which typically takes 3 weeks at a Royal Australian Air Force base in their home state . Upon successful completion of the cadet under officer course , cadet under officers are given full Officer privileges , which includes the right to use the officers ' mess on military establishments . New Zealand . Cadet under officer is also a rank in the New Zealand Air Training Corps and the New Zealand Cadet Corps . It ranks between cadet warrant officer and pilot officer NZCF or second lieutenant NZCF , thus making it the highest rank a cadet can reach , although not actually itself a cadet rank . Under officers are normally aged between 18 and 21 , and to be eligible for a commission one must be at least 20 years of age . Under officers are cadets who have received the necessary training and have the desire to become NZCF officers . Hence , under officers are treated as understudy officers . There are 2 under officers ' courses run each year , and provide the training that under officers require to be efficient understudy officers within their cadet units , and skills which will be useful as a commissioned officer . They perform roles similar to commissioned officers , but do not have nearly the same legal responsibilities and are not to be saluted , but are referred to as " Sir / Ma ' am " . Cadet under officers wear insignia similar to that worn by officer cadet s , except that the thin blue braid is replaced by a piece of NCO chevron cloth . This emphasises their official status as cadets rather than adult leaders . To become an under officer , cadets are required to : United Kingdom . Under officer is an appointment held by senior officer cadet s at the Royal Military Academy Sandhurst ( RMAS ) and in the University Officers Training Corps ( although these latter are not strictly trainee officers ) , and is also the highest rank that can be held by cadets in the Combined Cadet Force and Army Cadet Force . There are two separate appointments : junior under officer ( JUO ) and senior under officer ( SUO ) . They are usually addressed as " JUO " or " SUO " as appropriate , but are not saluted as they do not hold the Queen ' s commission . RMAS typically appoints two JUOs per platoon in the final term of the commissioning course . The appointment of SUO is not currently used at RMAS . At RMAS and in the UOTCs , JUOs wear an Austrian Knot above a single bar on their rank slide and SUOs wear an Austrian Knot above two bars . The use of the term in CCF contingents is inconsistent , with some having JUOs and sometimes also SUOs , and others simply having under officers . The ACF only has the single appointment of cadet under officer ( CUO ) . The rank badge is a white bar on the rank slide . The rank of adult under officer is an appointment used within ACF counties with adults who are progressing a commission . This appointment is at the discretion of the cadet commandant and is represented by a rank slide bearing a single white stripe . The form of address for all cadets , and adults at or below the rank of SMI is ' Sir ' or ' Ma ' am ' .