There are unsolved physical limitations to that with no solution in the near horizon AFAIK, the energy density of batteries is simply to low (energy per kg) for airplanes to be efficient.

> from underserved regional airports sooner than you think, doing routes and speeds comparable to High Speed Rail (and with comparable efficiency) but much more granular and without massive infrastructure

I didn't understand that, is there a limitation for using normal jet fuel planes from regional airports?