While many people concerned about climate disruption have changed their cars and their diets, few have changed their flying habits. The greenhouse gas emissions from air travel often blows away all the carbon savings from other lifestyle changes. That could be about to change. The airline industry has agreed to an international deal to reduce its greenhouse gas emissions.

What new fuels and technologies will make that possible? Can we really look forward to guilt-free flying in the foreseeable future? A conversation about cleaning up the skies and the possibility of going to see grandma on a jet powered by food scraps and old tree branches.