▁without ▁an ▁air worth iness ▁release ▁such ▁as ▁a ▁Supp lement al ▁Type ▁Cert ificate ▁( ST C ) ▁or ▁Part s ▁Man ufact uring ▁Appro val ▁( P MA ). ▁ ▁There ▁are ▁a ▁number ▁of ▁other ▁methods ▁of ▁comp liance , ▁including ▁parts ▁manufact ured ▁to ▁government ▁or ▁industry ▁standards , ▁parts ▁manufact ured ▁under ▁technical ▁standard ▁order ▁authorization ▁[ T SO ], ▁owner - / operator - produ ced ▁parts , ▁experimental ▁aircraft , ▁field ▁appro val s , ▁etc . ▁ ▁P MA - hold ing ▁manufact ur ers ▁are ▁permitted ▁to ▁make ▁replacement ▁parts ▁for ▁aircraft , ▁even ▁though ▁they ▁are ▁not ▁the ▁original ▁manufact urer ▁of ▁the ▁aircraft . ▁ ▁The ▁process ▁is ▁analog ous ▁to ▁' after - market ' ▁parts ▁for ▁autom ob iles , ▁except ▁that ▁the ▁United ▁States ▁aircraft ▁parts ▁production ▁market ▁remains ▁tight ly ▁reg ulated ▁by ▁the ▁F AA . ▁ ▁An ▁applic ant ▁for ▁a ▁P MA ▁applies ▁for ▁appro val ▁from ▁the ▁F AA . ▁The ▁F AA ▁prior it izes ▁its ▁review ▁of ▁a ▁new ▁application ▁based ▁on ▁its ▁internal ▁process ▁called ▁Project ▁Prior it ization . ▁ ▁The ▁F AA ▁Order ▁covering ▁the ▁application ▁for ▁P MA ▁is ▁Order ▁ 8 1 1 0 . 4 2 ▁revision ▁D . ▁ ▁This ▁document ▁is ▁word ed ▁as ▁instructions ▁to ▁the ▁F AA ▁review ing ▁personnel . ▁ ▁An ▁accomp any ing ▁Ad vis ory ▁Circ ular ▁( AC ) ▁ 2 1 . 3 0 3 -