Taxes need to be internationalized to prevent tax havens and other such behavior which work to undermine serious attempts to address problems that need to be addressed through progressive taxation and other taxes on the wealthy and capitalist. We need more international regulations and governance, not less. It's time we realize that.
Air travel is already something that many people find too expensive. If there was an international flight tax, it would probably only serve to drive the price of tickets up and up. There is no good reason why people should have to pay more money for an already expensive flight. I don't see why it would be beneficial to be an international tax either. People from poorer countries should pay less.