Politicians in general are jumping on the environment bandwagon because they think that it'll be vote winners. A big mistake IMO because at the end of the day people are more likely to vote with their pockets. People are already fed up with the 'hidden' charges added when booking a flight, so they are hardly goinging to be enamoured into voting for someone who proposes to charge more.
Besides, I would prefer to get the airport two hours before my flight and hang around waiting, rather than take the train.