Singapore Air's place in this list depends on your nit-picking definition of what an "airline" is. Their SilkAir subsidiary operates narrow-body Airbus 319s and 320s. Should the way they've chosen to structure their corporation for financial and marketing purposes matter, or is the only thing that matters that you won't see a narrow-body with their golden winged lion on the tail? I don't have the answer, just raising the question.