"China = 1.5 billion passengers and the world’s second largest economy.
India = 1.2 billion passengers and the world’s third largest economy.
FSU (Former Soviet Union) = 480 million passengers and the world fifth largest economy."
Such things are notoriously difficult to define. However, even Ryanair would be hard pushed to get enough money out of 1.5 billion Chinese, 1.2 billion Indians or half a billion FSUvians to define them all as potential (let alone actual) passengers. If you want a plausible definition of where the bodies are, what sort of money they might have in their pockets, and how they're thinking of spending it when they've fed, clothed and taught their kids, take a look at the various 'next billion' analyses that the mobile phone industry currently churns out.
See you in Shenzhen...
R