Today I Learned

Your assumption that busses exist so they can be improved is quite telling. Huge swaths of the population, even living in million inhabitants+ cities, simply are not served by any form of mass transit.

The reason public transit works so well in Germany (where I did live for a bit) and Holland (visited and read about) is not because taking a car is more expensive. It's because mass transit works well, it's there when you need it, gets you to your destination in reasonable time and comfort, and is easy to use.

The very urban fabric in the USA is car oriented. Every little bodega has to have a dozen parking spaces built by law. Supermarkets have 3 to 4 times their store area wasted in parking lots. Everything is far apart because of this, so walking is impractical. With everyone driving to places, you need wide, fast roads, which makes biking places very unsafe. Every once in a while I see a white painted bike attached to a memorial in a light post, commemorating a life lost. And I live in the suburbs.

It's not an insurmountable problem, the Netherlands did that in the 70s. But any solution that proposes a simple fix is doomed to failure. This has to be a concerted, intense effort to work.

My approach would be to jack up vehicle registration fees. Simply doubling the vehicle registration cost every year over about 5 years would make individual car ownership expensive enough that people will really try to avoid it.

By the fifth year you're looking at about $5k per year just to legally own and operate a car on public roads, which is workable (most people pay more than that per year for their car loans) but it's more than enough to make any family think twice about owning more than one car, and more than enough to make not owning a car and just renting/taking public transit a super attractive option. Plus it's more than the cost of a mid-range e-bike so trading your car for an ebike becomes extremely cost effective with a break-even point measured in just months

5 years is also enough time to get roads reconfigured for the new traffic flow of mostly ebikes, get more buses in the roads and start planning/building out new train routes. There's an incredible rail network still in the US and just putting out more passenger services on the existing tracks that are presently freight-exclusive would make a massive difference

Weight. As you burn down fuel, the plane gets lighter, so requires less fuel/energy for the remaining distance.

With a battery powered plane, the battery is just as heavy all the time. It also has less energy density. This means wayyy less range with current tech.

Technology, or rather, lack thereof. As others pointed out, planes need to bring their own energy supply and use additional energy for that. Weight is a very big factor for air transport's energy consumption. Fossil fuels have a very high energy density, which make them great for bringing along. Once light weight battery tech (without excessively large sizes) becomes available, it should be no issue to electrify planes. Alternatively, find another source of electricity. E.g. nuclear has a much higher energy density than fossil, but obviously has it's own issues, as do all other currently available tech options.