[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.

[crote]

If we do simple extrapolation, a cellphone-sized battery will reach the 80kWh needed to power a car in as little as 180 years.

Expecting a 5% / year growth rate sustained for 30 years is very optimistic. It is far more likely that we'll hit some kind of diminishing return well before that.