As for uniquely coding aviation ULBs - there's not a lot of point since, unlike with tagged animals, in any given ocean in any given 30-day period it's hardly likely that there will be more than one pair of ULBs down there!
But if an aviation ULB can't be distinguished from a similar device attached to an animal, you're depending on the aircraft crashing in an area where there aren't likely to be any tagged animals?