Liquified hydrogen is the best possible fuel for aircraft, newly practical since advances in aerogel production that make well-insulated tanks practical.

It will unfortunately need new airframes, because even liquified it needs a fair bit more room than diesel. But once those are going, nobody will be able to compete with them. The hydrogen can be produced right at the airport from solar electric at minimum spot prices.

With this development, some of it can be produced without the round trip through electrics.