Ultimately, to achieve the desired reduction in aviation emissions will require a basket of measures advanced through a mix of public policies, including information, incentive and directive-based approaches. There is not silver bullet. Different blends of policies would be required at different stages of technology maturity. Given the long lead times and risks involved in the new technological development, goverments have a key role to play in de-risking incentivising and 'pushing' the low-carbon transformation.