Easyjet has made the remarkable observation that if you raise the price of something, with the intent of deterring people from purchasing it, then this deters people with a little money more than it deters people with a lot of money. Who would have thought it?
Like it or not, unless we can find some way of powering planes without emitting carbon dioxide, over the next few years air travel must go back from being a cheap commodity to being an expensive luxury. And whichever way you cut it, poor people can’t afford luxuries. :-( There’s only so much improvement you can get out of more efficient planes. Eventually, you have to do things which mean that there are fewer flights, and so fewer seats, and so (given constant or rising demand) higher prices.
Incidentally, planes are not “public transport” in the normal sense. Public transport is transport you take as an alternative to private transport – i.e. cars. Its existence and use is encouraged because it is better than a car in one or more ways – e.g. lower fuel use per passenger, less congestion, more accessible to the poor, higher capacity. But only for very short flights are plane journeys alternatives to car journeys. For long-distance trips, they are the only game in town.
So when someone suggests removing the tax exemption on aviation fuel, complaints of “but other types of public transport get more subsidy than we do anyway” don’t wash.