▁and ▁K FI ▁in ▁Los ▁Angeles , ▁among ▁many ▁others , ▁have ▁been ▁permitted ▁to ▁keep ▁their ▁original ▁or ▁re ass igned ▁three - letter ▁call ▁signs . ▁In ▁addition , ▁a ▁new ▁or ▁existing ▁station ▁may ▁adopt ▁a ▁three - letter ▁call ▁set ▁if ▁they ▁have ▁a ▁sister ▁radio ▁or ▁TV ▁station ▁in ▁that ▁market ▁with ▁those ▁calls ▁( examples ▁include ▁W J Z - FM ▁Baltimore ▁and ▁W G Y - FM ▁Alb any , ▁New ▁York ). ▁( Note ▁that ▁stations ▁lic ensed ▁in ▁Louisiana ▁and ▁Minnesota , ▁the ▁two ▁states ▁with ▁significant ▁territory ▁on ▁both ▁sides ▁of ▁the ▁Mississippi , ▁are ▁allowed ▁to ▁use ▁call ▁signs ▁starting ▁with ▁either ▁W ▁or ▁K , ▁regardless ▁of ▁their ▁location ▁with ▁respect ▁to ▁the ▁river .) ▁In ▁av iation , ▁grand father ▁rights ▁refers ▁to ▁the ▁control ▁that ▁air lines ▁ex ert ▁over ▁“ sl ots ” ▁( that ▁is , ▁times ▁all otted ▁for ▁access ▁to ▁run ways ). ▁While ▁the ▁tr end ▁in ▁air port ▁management ▁has ▁been ▁to ▁re assert ▁control ▁over ▁these ▁sl ots , ▁many ▁air lines ▁are ▁able ▁to ▁retain ▁their ▁traditional ▁rights ▁based ▁on ▁current ▁lic ences . ▁ ▁In ▁the ▁UK , ▁until ▁ 1 9 9 2 , ▁hold ers ▁of ▁ordinary ▁car ▁driving ▁lic ences ▁were ▁allowed ▁to ▁drive ▁bus es ▁of ▁any ▁size , ▁provided ▁that ▁the ▁use ▁was ▁not ▁commercial ▁and ▁that ▁there ▁was ▁no ▁element ▁of ▁" hire ▁or ▁reward " ▁in ▁the ▁vehicles ' ▁use ; ▁in ▁other