▁Aer onaut ical ▁terms ▁ ▁Prior ▁to ▁ 1 9 6 9 , ▁air worth iness ▁standards ▁for ▁civil ▁aircraft ▁in ▁the ▁United ▁States ▁Federal ▁A viation ▁Reg ulations ▁specified ▁that ▁distances ▁were ▁to ▁be ▁in ▁stat ute ▁miles , ▁and ▁spe eds ▁in ▁miles ▁per ▁hour . ▁In ▁ 1 9 6 9 , ▁these ▁standards ▁were ▁progress ively ▁am ended ▁to ▁specify ▁that ▁distances ▁were ▁to ▁be ▁in ▁na ut ical ▁miles , ▁and ▁spe eds ▁in ▁kn ots . ▁ ▁The ▁following ▁abbre vi ations ▁are ▁used ▁to ▁distinguish ▁between ▁various ▁measurements ▁of ▁air speed : ▁ ▁K T AS ▁is ▁" k not s ▁true ▁air speed ", ▁the ▁air speed ▁of ▁an ▁aircraft ▁relative ▁to ▁und ist urbed ▁air ▁ ▁K I AS ▁is ▁" k not s ▁indicated ▁air speed ", ▁the ▁speed ▁shown ▁on ▁an ▁aircraft ' s ▁pit ot - static ▁air speed ▁indicator ▁ ▁K C AS ▁is ▁" k not s ▁cal ibr ated ▁air speed ", ▁the ▁indicated ▁air speed ▁corrected ▁for ▁position ▁error ▁and ▁instrument ▁error ▁ ▁K E AS ▁is ▁" k not s ▁equivalent ▁air speed ", ▁the ▁cal ibr ated ▁air speed ▁corrected ▁for ▁ad i ab atic ▁compress ible ▁flow ▁for ▁the ▁particular ▁alt itude ▁ ▁The ▁indicated ▁air speed ▁is ▁close ▁to ▁the ▁true ▁air speed ▁only ▁at ▁sea ▁level ▁in ▁standard ▁conditions ▁and ▁at ▁low ▁spe eds . ▁At ▁, ▁an ▁indicated ▁air speed ▁of ▁ 3 0 0 ▁kn ▁may ▁correspond ▁to ▁a ▁true