I'd read a comment in another thread saying that United, for example, gets maintenance done in El Salvador, with a single FCC-certified mechanic in charge of a

I'd read a comment in another thread saying that United, for example, gets maintenance done in El Salvador, with a single FCC-certified mechanic in charge of a team of non-certified people, whereas American maintenance is US-based with teams that are mostly-certified. So there's room in the rules for variation that could matter a lot.