Starting 1/1/12 Europe will impose a cap-and-trade system on airlines to reduce their greenhouse gas emissions. Airlines will initially get free permits to cover 85% of their existing carbon-dioxide emissions but will have to buy any additional permits. While the permit price is still TBA, it seems it will be based on a price of €13 ($16.5) /ton of carbon dioxide; adding about €2 to €12 per ticket depending on distance.