Yes, it is possible to have multiple patrons for a subject. Don't worry about a "right" answer. Sometimes the assignments are rather arbitrary.
For example, I suspect St. Joseph of Cupertino was chosen because he was known to levitate (i.e. fly). Really, there is probably no reason to suppose he's any more effective than anyone else in praying for flight attendants. He just got "stuck" with the job.
RE: Our Lady of Loreto. I am not 100% sure why, but the legend goes that the house of the Virgin Mary was miraculously transported by angels from Nazareth to Loreto. (As it turns out, the "angels" were a family literally named "Angelo" who transported it a more prosaic way.) Perhaps the mistaken legend of the "flying house" led to the association of Our Lady of Loreto with flight attendants.
Of the three of these, the only one I can see that has anything meaningful to do with flight attendants is St. Bona of Pisa, who in her life, actually helped travelers on pilgrimage.
My bets would go with her.