What if they were to win? that is, Plane Stupid were successfull? Either no flights or the majority are priced out of being able to fly.that would mean that this one process that releases Co2 stops. 3 (ish) % of emissions are saved. But outside of this the world of work (making profits) continues, the underlying reason for the big, really big emissions continues, and grows. Whilst one of the safety valves of individual people doing this work, going on holiday, is closed. The world becomes smaller, except for those with the income. And in the process of doing this large swathes of the population are alienated from the possibility that green politics has something to offer them other than 'less' or 'worse', no solidarities are built up, no movement with demands that you can really imagining spreading like wildfire.
And this very process of the reduction of CO2 will only leave the state and capital stronger. As their solution is : more tax on 'non essential travel'. So who decides what is 'non essential'? the UK state would. That's the same state that dismantled public transport networks, smashed domestic coal meaning that 70% is imported over vast distances, facilitated the exodus of manufacturing from here (where potentially we could implement greener production techniques) to the East, the same state that consistently refuses to invest on the massive scale needed for a renewable infrastructure.
And what would 'essential travel be? movement that makes more profits, and for people with enough money to pay the tariff. Be careful what you wish for.
Free spirit - if the wordyness of that text is getting on your nerves then have a look at the 'capitalism and climate change' slideshow here:
http://freelyassociating.org/downloads/