In the medium term, contrails and contrail-cirrus can be reduced substantially by ATM action In a similar or shorter timescale, EINO X of new production engines can be reduced substantially Neither is likely to happen without regulatory action Regulatory action is unlikely without a better scientific understanding of climate impacts of contrails, cirrus and NO{sub}x In the long term, reducing CO{sub}2 is the main environmental goal Manufacturers have large 'mainstream' R&D programmes aimed at reducing fuel burn - fuel price is a key driver Some areas of high promise, notably laminar flow control and multistage long-haul travel, appear to need stronger incentives to generate the necessary R&D commitment.
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