Kinda crazy but might actually work for continental flights over cooperative areas. Parachute the empty batteries down with some minimal steering mechanism to land them at regularly spaced depots, then ship them back to airports fully charged.
Turnaround time for planes is short enough that you’d need to do a battery-swap rather than a battery-charge anyway.
Turnaround time for planes is short enough that you’d need to do a battery-swap rather than a battery-charge anyway.