Comment by rgmerk

Hmmm. If we do simple extrapolation based on a battery density improvement rate of 5% a year, it takes about 30 years to get there. So it's not as crazy as it sounds - and it's also worth noting that there are incremental improvements in aerodynamics and materials so that gets you there faster...

However, as others have pointed out, the battery-powered plane doesn't get lighter as it burns fuel.