I don’t have a problem with developing aircraft that can operate on alternative fuels. After all, a turbine engine can run on almost any liquid that will burn. My issue is what is the source of the alternate feedstock and can they produce the fuel in sufficient quantities to meet the demand? Properly processed in a hydro-cracking unit, the alternate fuel can be virtually indistinguishable from petroleum jet. But, much of those feedstocks are either plant based (eg. Soybeans) or waste cooking oils or animal fats from meat processing. Hardly reliable sources of fuel in times of war.