My understanding is that the 4680 cell doesn't have any better energy density than what Tesla is currently using (the 2170). Yes, it has 5x the energy of the 21

My understanding is that the 4680 cell doesn't have any better energy density than what Tesla is currently using (the 2170). Yes, it has 5x the energy of the 2170 but it's also 5.5x bigger in volume. In essence, the energy density of the cell has gone down, not up. The battery as a whole could still go up because bigger cells mean less weight in the steal casing, better packing efficiencies and the tabless-ness of the 4680 should allow more efficient thermals. I'm assuming that the claimed 16% improvement in range would come from that. The big improvement of the 4680 is the power (and manufacturing costs), not the energy. In any case, it's sort of a moot point if Tesla won't sell these batteries/cells to anyone else. Anyway, my take on the article was that the practicality of the electric airplane basically comes down to battery tech. If someone produces a dramatically better battery I assume that putting it into an airplane will be straightforward. So if you want to build an electric airplane what you should really be building is a better battery.