It's impossible for electric planes to be cheaper than electric rail - everything about a plane is harder to achieve, the size will be smaller (since it also needs to lift off the ground, not just drive), safety is a much bigger concern (leading to much more time for boarding procedures). The only advantage air travel has is that it doesn't require real-estate.
Instead, electric planes still need decades of engineering work, and what we know for sure is that they will be less efficient than kerosene planes, as there is no type of battery even plausible today that could achieve anywhere near the energy density of gasoline (in Wh/kg, not Wh/l as is sometimes shown).
