hydrogen seems a good fit here. the extraction process can be sustained from renewable or low emission sources, refueling danger risk can be mitigated since the

hydrogen seems a good fit here. the extraction process can be sustained from renewable or low emission sources, refueling danger risk can be mitigated since these planes are not meant for general populace access. how much safety is of a concern depends on application. for fully autonomous cargo planes you'd already reduce it significantly and can be improved further by routing them around and not above densely populated areas. they'd be highly situational, but for those routes they could be approved for they'd be great.