3. Exotic materials like aluminum and carbon fiber? The BMW i3 adopted the latter for example
4. A better way to look at it isn’t whether air transport will ever be cheaper, but whether air transport can be cheap enough to be worth it due to the unique advantages it offers. Eg flying in a straight line, flying faster, no traffic, relatively easy autonomy compared to ground, etc
2. This entirely depends on the speed. For high speeds an airplane can be more efficient than ground based transportation. See von Karman efficiency, eg : https://www.researchgate.net/profile/Omer-Kinaci/publication...
3. Exotic materials like aluminum and carbon fiber? The BMW i3 adopted the latter for example
4. A better way to look at it isn’t whether air transport will ever be cheaper, but whether air transport can be cheap enough to be worth it due to the unique advantages it offers. Eg flying in a straight line, flying faster, no traffic, relatively easy autonomy compared to ground, etc