Atmosfair have published the first airline climate index ranking international air carriers according to CO2 emissions per flight kilometer and passenger. Taking into account factors like seating capacity per plane (the higher, the better for CO2 efficiency), load factor and aircraft types in use, the ranking offers surprising insights: No airline qualifies for the top two efficiency classes. And even then the highest ranks are occupied by any but the major carriers. Two charter airlines from the UK and Germany lead the pack, with the first major airline (carrying more than 20 million passengers a year), Korean Air, coming in at 20th place.

Here's the link to the full airline index, plus another link to the document outlining atmosfair's methodology.