Well the company states that the batteries (each 1000kg) are loaded into the wings of the plane, and that the wings will be significantly larger than that of current commercial aircraft, with a passenger count of like 90, and for only 1000km. So you're right, there's definitely a limit, however it still seems like a viable technology.

I remember sitting around the table after a thanksgiving dinner with all my conservative relatives, who were making fun of electric cars, and I said the same thing to them that I'll say to you now. It all starts with a little innovation, that can form a link in the energy chain. Once people prove it can be done, then it will be improved, and improved, until it's no longer a technological marvel, it's just a Tuesday. One day we'll have gas powered crafts purely as collectors items and antiques, and an entire green grid. but you gotta start somewhere.