Presumably once Tesla's "gigafactories" kick into gear they will use Tesla cells. This is starting to "take-off" (pun intended) because the energy density/weight ratio of batteries is starting to become halfway reasonable. You still take the penalty of having a heavier airplane compared to a fuel airplane (to accomplish the same mission) but it costs significantly less to operate. Expect operating costs to get even lower as the technology progresses.They must be using some new tech batteries. What these might be? What's in E-aviation?