By avoiding air travel altogether, you’re doing the environment a huge favor. The problem is avoiding airplanes and using alternative forms of transportation isn’t always possible, especially if you have to make it overseas. Still, you can make a difference by traveling with the airlines that pollute the least. According to a new report, EasyJet is top of the league when it comes to airlines trying to cut carbon emissions, with data suggesting that by 2020 its emissions per passenger kilometer will be less than half that of some rivals. Alaska Air, Qantas, United, and JetBlue are next in line in terms of lowest carbon emissions. On the flip side, the report names Air China, Turkish Airlines, Korean Air, and a number of others for having the weakest plans for lowering emissions.