Airlines will be able to declare the fossil fuels they burn to be green 'alternative fuels' under a UN scheme set up to tackle the climate impact of flying. For example, airlines burning kerosene could be rewarded with reduced obligations to buy carbon offsets simply because the refinery producing the oil was running on renewable electricity. The agreement on which fuels will be credited under the scheme, which is known as CORSIA, was reached last night at the UN aviation agency ICAO in Montreal.