The quest for guilt-free flying may have been knocked off course by a broad study that has concluded there is "no clear or single net zero alternative to jet fuel".
The four most viable alternatives "offer some carbon savings but are not ideal", according to the review by the Royal Society academy of scientists.
Replacing jet fuel with biomass, for example, would require half the UK's farmland just to sustain current passenger levels.
But the government is planning for levels to soar by 70% by 2050, representing an additional 200 million passengers.
Here is the link to my Radio Interview with BBC Radio Scottland on what we can do realistically from now until 2050 to decarbonize the aviation industry.
https://www.bbc.co.uk/sounds/play/m001jjmn