for them to be part of air travel in the future? a sustainable fuel is one where we extract the carbon from the atmosphere in a relatively short time before the fuel is burned, and so we end up with a net zero loop. so we take the carbon out of the atmosphere, put it into the synthetic fuel and then burn it in the engine. i haven t actually added any carbon to the atmosphere. and we are here with our technology ambitions, we know we can do it from a technology point of view, but we need governments to buy in now with the right sort of policies that enable this to become a reality. air travel has been transformational for humankind, but of course it has damaged the environment, which i think is something you have said before as well. do you accept any responsibility as one of the world s biggest aeroengine manufacturers for causing some of that damage? well, i think of course we must accept some responsibility for that