In the case of Trading names and the like, it is my understanding that unless JetStar Airlines (virtual) had already registered the name in Australia, then the name was available for anyone to pickup and use.
A well known example in Australia is the case of Burger King, who when they intially wanted to start trading in Oz (many years ago) could not do so as some enterprising "entrepreneur" had already registered the name. They subsequently traded under the name of "Hungry Jacks" for some time. Burger King now trades in Australia under the Burger King name, however I did read that some money changed hands to "buy" the Australian rights to the name.
My point is that it seems to be a matter that can only be dealt with in an Australian jurisdiction and it may be that Qantas were the first to register the name and form a legal entity based on that name, in Australia. Therefore it's theirs....in Australia.
Would be interested to read other points of view.