The battery energy density isn't there yet for electric air transport. During the June 2017 AGM, Elon said it'll be 5 years (2022) before Tesla has 500 wh/kg batteries in production (start listening at 3:04):
Notice that Elon didn't say "Panasonic?" Notice that he said "we?"
I think the Maxwell acquisition has been on his mind for some time. 400 wh/kg makes electric flight possible with
"substantial innovation in the airframe. At 500 it starts to become quite compelling."
Personnally, I think the new "Giant-Cube" Grohmann machine builds 'Maxcells', and soon we'll all be swimming in Tesla Semi's, Pickups, Model 2s, and FCF...
Cheers!