I think it's hard, yes. But I also think forever is a long time. ;) You certainly can't get there by taking an existing aircraft, removing the fuel and replaci

I think it's hard, yes. But I also think forever is a long time. ;) You certainly can't get there by taking an existing aircraft, removing the fuel and replacing it with batteries. It's the same fallacy as the gasoline automakers make with electric cars, and it results in a worse vehicle design. The whole system has to be re-imagined from the ground up to exploit the advantages of electric propulsion. Several of the design concepts for his proposed supersonic VTOL electric transcontinental commercial jet airplane have already been revealed: * The plane would fly at high altitude, somewhere around 80,000 ft. Combustion airplanes have a 30-40,000 ft ceiling limited by the need to ingest oxygen. Due to the exponential decay of density with height this dramatically reduces drag, thereby reducing engine power and structural stress. Coincidentally this is also higher than almost all bad weather. * VTOL is easier since electric motors have a better power:weight ratio than turbine engines. This eliminates constraints due to runway length and width, and means the wing can be more closely optimized for cruising. It also means smaller airports are possible, reducing gate fees. * The wings also don't need to double as liquid fuel tanks, and don't need to handle different stresses when empty vs full. * A high mass fraction of batteries compared to combustion aircraft (mid to high 70% range). Energy density at least 400 Wh/kg (which as you point out, is still much lower than kerosene). * Eliminating the tail section in favor of gimbaling the electric fan, again reducing drag and weight. * You also get about a 1% drop in weight compared to existing jets due to reduced gravity and centrifugal force. A good video compilation of quotes is https://www.youtube.com/watch?v=erjdYiwoYAo https://www.youtube.com/watch?v=erjdYiwoYAo