Every year, the kWh/weight of lithium ion cells has been increasing by around 8%. This means that the same charge would require 1/3 less weight every five years.
Electric aircraft exist, but they are too limited in range and are expensive.
Electric aircraft have the advantage of not experiencing power loss at altitude. If an electric aircraft can climb to 28000ft it will fly 50% faster than a sea-level plane using the same amount of electrical power. An electric aircraft could theoretically be built for supersonic flight at high altitudes, where the speed boost can reach 200% or more. Elon Musk claims he would like to create one.
I believe small electric aircraft, with a range of over 1000 km, will be a good idea once Lithium Ion’s weight and kWh/weight increases by two in approximately a decade.
It is possible to accelerate the development of a better battery technology.
We should see the first electric aircraft for two-seaters with 400+ km range in 5 years.
These aircraft will likely also be equipped with solar cells that will improve range up to 20% for flights in broad daylight. A solar powered glider or aircraft with large wings could give you an even greater boost.
This could be accelerated by the Tesla Gigafactory.
Edit: It’s 2020. Electric aircraft are already popular and cheaper to pilot train than a Cessna. This is because electricity is so much cheaper than AvGas or MoGas. E-Biz planes have a 1500km range and there are prototypes.
It’s happening quicker than I thought. We should have an electric aircraft prototype capable of carrying 150 passengers with a range of 500 km by 2025. It will eventually surpass the 2000km mark and compete with the small-bodied fossil airliner market.
It could be Lithium CO2 that is the technology to do it. They’re talking about 7x the energy density of current Li Ion batteries. Practical short-range transport e-jets would be feasible if they had 3x the current Tesla battery pack tech energy density.