Ways to make aviation fuel green

is by no means the biggest source of anthropogenic greenhouse-gases. At the moment, it contributes about 2.5% of them. But, after a covid-induced dip, air travel is once again growing (see chart), and its emissions are high-profile and hard to deal with. For short-range, small-capacity planes batteries show some immediate promise. But for bigger aircraft the technofantasy of using compressed hydrogen (made from green sources, natch) either as jet fuel in its own right, or to run fuel cells which then drive electric motors, is likely to remain just that—a fantasy—for decades.