The 'tax' would penalise those who are more reliant on air travel due to geographic reasons (island nations such as Ireland, Britain, etc). If they are so gung ho on solving the world's problems, then why don't they slap the tax on all transport modes, including train fares and toll roads!
Between fuel surcharges, airport security, car parking fees, national taxes, etc, the cost of an airline ticket is now a multiplier of the actual fare itself.