u will never never know
unfortunately unless u r are recruiter or a good friend of a recruiter u will never really know.
Their are many things that the airlines look for, some like Emirates discriminate heavily, others want a broad mix of people.
Virgin Blue for instance recruited very young and attractive, but that seems to have changed as most people are concerned for safety. That been said, young ones and attractive ones are not necessarily stupid.
Their are certain occupations that "trigger" a certain interview this person,a nd the occupations are quite surprising. Not the hotel, waiter/tress, bar man/girl receptionist, etc..... these are what most of us feel as typical customer service positions.... yet would u believe, that firemen, paramedics and very very high are Nannies and Nurses. If u r one of these and present well, u can just about pick your airline.
hope this clears matters!