▁Maryland , ▁in ▁April ▁ 1 9 4 7 , ▁was ▁promoted ▁to ▁captain , ▁and ▁became ▁part ▁of ▁the ▁U . ▁S . ▁Air ▁Force ▁when ▁it ▁became ▁an ▁independent ▁service ▁on ▁September ▁ 1 8 . ▁ ▁G arrison ▁organized ▁and ▁led ▁a ▁jet ▁aer ial ▁demonstr ation ▁team ▁for ▁the ▁ 4 th ▁F W , ▁flying ▁P - 8 0 ▁Sho oting ▁Stars , ▁and ▁participated ▁in ▁the ▁first ▁official ▁delivery ▁of ▁air ▁mail ▁by ▁jet ▁to ▁celebr ate ▁the ▁ 3 0 th ▁anni versary ▁of ▁air ▁mail ▁on ▁May ▁ 1 5 , ▁ 1 9 4 8 . ▁Using ▁the ▁same ▁route ▁as ▁in ▁ 1 9 1 8 , ▁G arrison ▁delivered ▁a ▁packet ▁from ▁Washington , ▁D . C . ▁to ▁New ▁York ▁City ▁in ▁a ▁ 2 8 - min ute ▁flight . ▁In ▁May , ▁ 1 9 4 9 , ▁he ▁led ▁the ▁team ▁representing ▁the ▁ 4 th ▁F ighter ▁Wing ▁at ▁the ▁first ▁Air ▁Force ▁World wide ▁G unn ery ▁Compet ition ▁at ▁Las ▁Veg as ▁Air ▁Force ▁Base , ▁Nev ada , ▁winning ▁the ▁jet ▁portion ▁of ▁the ▁competition . ▁ ▁G arrison ' s ▁noted ▁g unn ery ▁skills ▁and ▁prior ▁instruct or ▁experience ▁resulted ▁in ▁his ▁transfer ▁in ▁May ▁ 1 9 5 0 ▁to ▁Las ▁Veg as , ▁now ▁Nell is ▁Air ▁Force ▁Base , ▁where ▁the ▁US AF ▁converted ▁its ▁flying ▁training ▁establishment ▁into ▁the ▁US AF ▁A ircraft ▁G unn ery ▁School .